Ethiopia 5 Gondar

IMG_7704Gondar was a dead loss as far as the Internet goes, I hardly got online at all.  We had a walk around the palace or castle which was really good because our guide was very good.  We had some lunch at the famous Master Chef which was just down our street and got our guide again to go to the church.  It is supposed to be the most decorated Ethiopian church and I believe it.  In the church grounds was an amazing variety of birds.  We saw huge ravens, vultures and lots of really colourful pretty birds.  We had a drink at our hotel and caught a Bajaj to a hotel at the top of a hill called Goha with fountains and an alga pool.  Back down to the other guide book recommended restaurant called the four sisters for dinner then home to bed.  An early start in the morning as we were picked up at 7.30 am to go to the airport to fly back to Addis.  IMG_7708We were both pretty knackered by now as we have had a demanding ten days.  Once we landed, we walked around to the international airport next door to check ourselves and our bags in so we didn’t have to drag them around all day.  Also it should make it easier when we go back to fly to London.  The taxis wanted 300 birr just to go to town so Georgina rang her friend at ETT travel and they sent a car for us.  The car took us around IMG_7721the red museum then for lunch at the most expensive Chinese I have eaten in.  They wanted 625 birr for chicken soup and there are 37 birr to the pound.  Following lunch we both started to feel wiped out and asked to be taken to a quiet place for a drink that wasn’t so expensive and he took us to Ghion hotel with nice grounds.  Once there he saw we were knackered and offered us a complimentary apartment what’re we could have a nap and relax before our journey home.  We couldn’t get online but it’s a place to relax and wind the hours down until they pick us up at 10:30 pm tonight.IMG_7745






Ethiopia 4 Lalibela

Very thorough check in we had to put bags through twice and both inspected.  Flight was DSCF3565less than an hour and our bags brought to door.  Someone had Georgina’s name on a card and took us to our hotel, the Top Twelve hotel.  Best rooms so far with proper shower and balcony.  We went to a restaurant called Ben Adana which is very unusual and the food divine.  I had spiced Ethiopian shepherds pie and salad, yum!  We went to the office to pay for tours and guide Tady which was very expensive and around the churches, finishing at St George’s cross.  Amazingly, we bumped into Mateus, the German and so arranged to meet for dinner at the Seven Olives Hotel.  I couldn’t resist the peppered steak.

Ben Adana Restaurant

Last day at Lalibela and even more churches to see.  There are eleven all together in town but we rented a minibus this morning to visit another one about 40 km away.  Of course lost of walking up hills for probably an hour, then we had to walk on a rough floor with no shoes on again for ages.  It doesn’t seem to affect the others like me because I have more weight on mine and they are covered in

Dik Dik’s playing

blisters.  Back to Lalibela to the museum which was quite interesting.  We tried to have lunch at our hotel but they only had a three course special so we went next door to the DSCF3579Paradise hotel for cheeseburger and chips which were really nice although a little pricey.  The afternoon was spent seeing the other churches around town that are

Ethiopian shepherds pie
Ben Adana

chiseled from the rocks.  I’m churched out now, they all look pretty much the same to me.  Another priest blessed us with his gold cross so we should be ailment free now.  We had to go to our favourite restaurant to watch the sun go down with a drink and then the Ethiopian shepherds pie.  What a place!
Saturday was a bit of a washout as they took us to the airport so early we spent most of the day there. Also we hadn’t paid for the hotel until we left so that left us both without much money.  When we finally

Georgina blessed

set off the journey was only 30 minutes and a car was waiting for us.  The hotel is a family run one and it’s ok butIMG_7647 not as nice as some of the others we have stayed in.  We dropped out stuff and walked a while to find five ATMs but none would give us money so we found a little dirty hotel for lunch and shared a pizza.  When we walked back the ATMs were working.  I didn’t feel very well so went to bed at around 5pm.  I woke every hour for the IMG_7656toilet so suspect it’s something to do with diabetes.  The church wailing started at 10:30pm and is still going at 7am when I finally got up.  Although frequently waking, I slept for most of the time.IMG_7675

Ethiopia 3 Aksum

We left Mekele around 9 am and visited a church that was cut from solid rock on our

Queen of Sheba Palace

way to Aksum.  Although the driver went quite fast we did not get there until after 1 pm and our hotel was almost full, only suites left so I rang Gerry and he came over.  There was a new one opened 6 weeks ago called Serina hotel so that’s where we are.  It’s literally next to Gerry’s shops and house.  I used to work with Gerry, years ago at Mertech.  There were four of us in the office, Chris was exactly ten years older than me and Gerry was exactly twenty years older than Jim.  When Gerry retired he came to live here in Axum Ethiopia as he married an Ethiopian lady while working here years ago.  They have seven kids who all live in IMG_7489Luton.  Unfortunately, Gerry’s wife died of cancer a couple of years ago.  He supports six Ethiopians with food, shelter and clothes.  He is building quite a few houses so they all have somewhere when he dies.  He also has five really nice shops next to his house.  We went to his house for traditional coffee then had lunch then went out in a Bajaj to see a few sights.  We saw the Ethiopian equivalent of the Rosetta Stone plus a highly painted church.  Although they are mainly author ax Christians, there are similarities to Islam.  Like the wailing they seems to be constantly coming from the churches.  Georgina and I had dinner at the nice hotel we couldn’t stop in then had an early night.  I woke as usual at 4am but found that I could use the Internet because nobody else was.  Finally got some postcards sent off.  Tomorrow we will be visiting the sights with Mr Gerry.  Back to sleep for me now for my second sleep.  See you in the real morning.

IMG_7496Mr Gerry did us proud, we had seen all the sights by 4 pm and that included a 2 hour lunch break and traditional coffee back at his house.  Aksum is to the Christian church what Mecca is to Islam.  The Muslims have been trying to build a Mosque here but they have been told that when we can build a church in Mecca, then they can build a Mosque here.  I particularly liked the museum, the old fella that looked at our paperwork guided us around and he really knew his stuff.  U fortunately, we couldn’t take photos inside.  There were two tombs actually inside the museum that were being excavated slowly.  One had already been done and lots of the artifacts were dug from this tomb.  In the evening we started by getting a Bajaj to the Yeha hotel where we had IMG_7506several drinks.  We even finished off the two bottles of red wine that I had carried up and down the volcano.  We then got a Bajaj back down into town and stopped at the Antika Cultural Restaurant where we both had fish goulash.  It was a bit like the Chinese dish crispy shredded beef but fish, very tasty but then again was the local beers.  We had one final beer back at our hotel and then to bed to sleep it off.  In the IMG_7514morning we packed and got a Bajaj to the Central breakfast cafe in town that we had spotted in the guide book.  I had my usual egg sandwich, tea but a fresh mango juice.  Georgina had the more traditional full which is spicy beans with eggs on the top with bread.  Our taxi hadn’t turned up so 15 minutes later we ordered another one to the airport.IMG_7523

Ethiopia 2 Active Volcano

IMG_7261We were picked up at 9 am and taken to the travel agent where they paired us all up into our land cruisers.  We had Elizabeth from Virginia but living and working  in Chad.  They gave us a list of stuff that we should take as its an extreme trip.  It was on the internet but we didn’t have enough to read it, or time.  I asked the driver to stop at a shop to get a towel as I hadn’t brought one.  It took ages but eventually found on for 300 Birr, a out £8.  We set off and it wasn’t long before we stopped for coffee and we could sort of meet the people from the other four land cruisers.  They are numbered 1 to 5 and we travel in convoy.  I was surprised that the IMG_7297roads were tarmacked.  In fact they were tarmacked most of the way.  We stopped for lunch, a sort of pasta and rice dish with vegetables.  They are fasting here at the moment and don’t eat meat.  They offer tuna to go on your pasta which always adds a little flavour.  It was many hours travel before we reached our camp but then we set off to the salt flats to watch the camel trains come by.  Incredible, mile after mile of salt flats and we could travel as fast as on the roads.  We set off again to the surfer fields but by now the temperature was 44 C in the shade.  And guess what?  There aint no shade.  Also the heat was reflected from the salt.  There was a long steep climb to reach the surfer fields with the pungent smell the whole way.  I haven’t brought a hat so used the yellow towel that I IMG_7307bought in Mekele over my head.  By the time we reached the duller I was feeling I’ll with overheating.  By the time I got down again I was feeling sick so he put the aircon on and I stayed in the car.  The next stop I missed by Georgina took some pictures for me.  We then moved on to a salt pool and people put there feet in.  It really turned out to be an unusual day.  Then we drive to the salt lake and I had a paddle.  By this time the sun was going down but not the temperature.  We sat in between two cruisers in the shade to wait for the sun set.  Out came the wine an Ouzo.  It really was turning out to be my kind of trip.  IMG_8962IMG_7312This is when you get to know the people with you, when the drinks start to flow.  Wine finished and sun set we set off back to base camp for dinner and more ice cold beers.
We are sleeping under the stars tonight in the open air.  They have some wicker beds and a blanket each.  I used mine as a pillow until I woke up cold then used my towel as a pillow and put the blanket over me.  I woke between 3am and 5am but then slept until 6am when we got up for breakfast.  The biggest challenge is that there are no toilets anywhere.  You have to walk off and squat.  IMG_9002Bloody nightmare.  I had to go at 3.15am which is quite normal for me and has the advantage that it’s dark.  It’s also a disadvantage as you have no idea how good is your aim as its not something you practice often.  Today we had a long drive of about 8 hours DSCF3526to get to the volcano.  We had quite a bit of off reading which was fun, especially the sand part.  When we got to a station they insist you have a guide to guide you through the lava field.  It was unbelievable.  30km over lava like Lanzarote, I wouldn’t have Camelbelieved it possible if I hadn’t done it.  Once at volcano base camp we had dinner and waited for it to get dark.  The plan was to ascend the volcano in the dark so it’s cooler and sleep on the rim.  Get up at 4am and go to look at the lava.  They didn’t think I could make the 11km hike so booked me a camel to go up on.  Cool ehh!  Climbing an active volcano on a camel at night.  The walkers set off but they had a real job getting me onto the camel.  Someone had to fetch a chair to stand on.  Once on I was completely unstable and it’s really high up.  I was gripping on for grim death and though I would never make 4 hours on it.  Twenty IMG_8929minutes later the camel sat down and refused to go any further.  I had to walk the entire way up in the dark without enough water and no torch as I had given it to George.  I was the last one up by over an hour.  Twenty to midnight when I got there.  I got a bed and went to sleep.  Four am as promised they wake us up to collect the beds and pack the camels while we went to see the lava as it was smokey at night earlier.  I didn’t go as I needed my morning routine.  This was a challenge climbing over volcanic rock to look for a suitable spot.  This is what my IMG_8942nightmares are made of.  Suitably packed up we set off in the dark again.  It was only 30 minutes or so before I could switch my torch off that I recovered from George.  I was completely exhausted by the time we got to base camp with the bottoms of my feet covered in blisters.  I can hardly walk at all now.  We had breakfast at base camp before the long treacherous drive back.  I couldn’t face breakfast only having water an melon.  I like there breakfasts normally, eggs with onions and spices, pancakes etc.  What IMG_8932a three day trip!  I have never been on anything like that before.  The towel was the best 300 Birr i have ever spent, i used it as a blanket, to sit on, to keep the sun off me and as a pillow.  Pretty much the only thing i haven’t used it for yet is to dry myself as i haven’t washed for three days.  I didn’t even take my clothes off either.  Quite surprised i couldn’t smell anybody, perhaps we all smelt as bad and we didn’t notice?  Tonight we will meet Mateus, a Fat old German that took a shine to me and always sits with me for food and IMG_8970drinks.  He has been off immense support to me as he gave me a hat and water on theIMG_7404 way down the volcano.  We went out for dinner with him when we got back.  I had peppered stick and chips, but i am glad to say it was a typo and was wonderful.  Georgina had fillet IMG_7399fish and fresh vegetables and chips and Mateus had fish goulash that he really enjoyed.  A few bottles of beer and all in a posh restaurant for about £10.  Tomorrow morning we will travel to Aksum to meet Gerry.

Ethiopia 1 Addis Ababa

As Georgina is working in South Sudan as a diplomat, I wanted to see her there but she thought it better if we met in Ethiopia, next door and had a holiday together there as it is much safer than South Sudan. The first chance we both had was March once my lectures had finished and prior to my thesis work starting.  Georgina had finished her MSc and

British Embassy

just about caught up with work so as last the time was here.  I caught bus from MK’s new coach way which was a few minutes late. Once I was dropped off at Heathrow main bus park it’s easy to walk to T2. Checking has evolved since I flew last year.  You do it at a terminal and it prints your boarding pass out and your bag label that you attach yourself.  Not sure if I was lucky but it seems to have eliminated the queues completely.  Here I am already through security with a couple of hours to go.  There is even a Ted Baker here, very upmarket.  Mohammad tells me there are three at Heathrow.  Georgina messages me already so I guess that she’s already in Ethiopia.  She will stay the night tonight but I won’t arrive until early morning.  Just had another message, Georgina has arranged a shuttle from the airport to her hotel for me.  It’s 3 hours ahead of here so 21:15 there so she will eat, do a little work and sleep.  I on the other hand have to sit here or on a plane until the morning and being so big I can never sleep.
We have the day in Addis to visit museums then fly to Mekele for the night but are staying in a cheap hotel.  The next morning, we are off on a three day treck around Danakil desert which is the hottest place on Earth and we can’t even wash so starting with a bang.

British Embassy

The flight started well, we boarded an hour before taking off, given free papers and headphones and could watch films immediately.  Well it’s still surprising me, could watch the film even when taking off and I have three adjacent seats.  We took off 15 minutes late but who cares?  It just keeps getting better, free red wine and snacks.  The wine is lovely, much better than the stuff I normally buy.  We also have a mean soon, probably with more wine.  Already watched, “Focus” with Will Smith, just trying “Run all night” with Liam Neilson.
We flew down the Adriatic Sea and over the south west corner of Crete, the old Myan grounds.   The food wasn’t to my taste (kid’s food) but the wine kept on coming. When it’s free, you have to make the most of it, but be subtle, hide empties until you don’t want any more.  Ask different girls for another one every time they come past.  Not quite sure how many red wines they gave me but they were very obliging and I managed to save two for another time. Arrived about 15 minutes late but managed to find the minibus to the Caravan hotel.  When I arrived, Georgina came out to greet me.  Altogether a pleasant trip.

Ethiopian Injera

We set off to the travel shop when they arrived at 9 am having had breakfast at Georgina’s hotel first.  Georgina settled up as I already transferred half to Georgina’s account before I left.  The guy that picked us up seemed to want to be our guide for the day and wanted to take the car to the phone shop so Georgina could get a local sim.  My phones locked so I couldn’t.  In Ethiopia they only have one phone company run by the government so it’s a real faf having to get passport picture and visa picture.  Georgina hasn’t got a visa as she is a diplomat but they didn’t recognise that so they couldn’t use hers.  I got the passport copy and had my picture taken so Georgina could get a sim.  Why does everyone laugh when I have my picture taken?  See, you’re doing it again now.
As it was a 2 mile walk and my legs had gone we got a cab to the British Embassy so that Georgina could drop off her two laptops for safekeeping until we come home next week.  They have golf and giant tortoises there, it’s a huge place.  I don’t think I have been to an embassy before.  Nice houses on the site as well.


We then got another cab back to the ETT car and drove to the museum where Arne and Lucy live.  3.3 and 3.2 million year old remains respectively live there.  What a treat, there are so many hominid remains at this museum, plus other normal more boring religious stuff.  They are mainly orthodox Christians here and there are churches everywhere.  There was one opposite the museum and they wail like they do at Islamic places.  And they do it every day for three hours.  Next stop food at the Lucy Restaurant on the museum site.  Yes, we could still hear them.  Georgina had a funny vegetable dish served on fermented flat bread.  I had lamb and chilies served on the same.  Very ripe and fruity.  We also got soup and bread to start and fresh fruit salad to finish even though we didn’t ask for them.  By this time we were running out of time as we were flying to Mikele at 6 pm and we needed to go back to the travel place to pick up our backpacks before going to the airport.  This still left us time to drive up the mountain to take some nice pictures first.

Mountain women

Lots of old ladies carrying piles of wood down the hill.  One old lady came to the car to beg as we were getting back in to leave.  I brought $100 dollars in $1 dollar bills for tips so I gave her one.  She seemed so excited and appreciative it was amazing.  She spat on my hand and kissed it.  Pew, did that stink.  It was ages before I could wash the bloody smell away.  Our drive said as we were driving away they she had realised it was a single dollar bill rather than the ten she had first thought.
We got to the airport, had a couple of beers and flew to Mikele in a prop plane that was full.  A driver with our names on a card was waiting to take us to the Stockholm hotel.  We dropped our bags and I had a quick shower.  The water was freezing.  I had switched the heater on but had no time to wait for it to warm.

Selem 150000y older than Lucy

There was no toilet paper but one of those squirty things they have in India.  It wouldn’t work until I switched the local tap on, then water squirted everywhere from leaking pipes before I even pressed the squirty.  I then braved the cold shower and just when i didn’t think it could get any worse, all the lights went off.  I had no idea where my phone or torch was as we had just arrived.  I fumbled around until I found my phone which helped me find the torch.  Only just got sorted out and the lights came back on again.  Seventy percent of Ethiopians do not have electricity but the other 30% only have it for half the time, that’s why they want to build this dam for hydroelectric power.
I went downstairs to find Georgina and we nipped out for a vegetable pizza.  Literally, with carrots, courgettes, mushrooms, spinach and pineapple; no cheese.  Funny, it was really nice with hardly any fat and they brought an accompaniment of mashed peppers and chilies.  Straight off to bed for my first sleep since I was in England a few days ago, but not before writing this up before I forget.  Early start in the morning as we are off in a bouncy truck to the hottest desert in the world where we are to climb a volcano.  Georgina has reserved a camel to take the old man up.  What a day, see you early in the morning.

Scanning Electron Microscope

I have always wanted to use a Scanning Electron Microscope (SEM) and my chance came last week at Cambridge University.  What a thrill.  I received an optical microscope for Christmas one year as a child and had endless fun and excitement with it, but the SEM is a whole new ball game and has a resolution down to 1.4 nm.   That’s a thousandth of a micron or a millionth of a millimeter. Hard to imagine.  To add to my excitement, it also had a focused ion beam (FIB) microscope adjacent to it that we used.  I didn’t even know what they were until a few days before we used it.  Its similar to the SEM microscope but fires ion instead of electrons which are much bigger and heavier so can inflict more damage.  When the current is turned up, you can machine or mill the sample in a very controlled and accurate way.  We also injected gas molecules (organic platinum) between the sample and the FIB.  If the current is just right, it won’t machine the surface but rather split the platinum from the organic part of the molecules and deposit them on the surface of the sample.  Because you have the SEM pointing at the same place you can look at what you have done.  I want one!

SEM with FIB at 54 degrees

You don’t think of a microscope firing a current, but that’s exactly what a current is, a flow of electrons.  To get an idea of how many electrons are being fired at the sample; A Coulomb = 1 Amp per second.  The charge of a single electron is around 1.6 x 10-19 coulombs so there are 1 / 1.6 x 10-19 = 6.25 x 1018 electrons per second for 1 Amp.  We have a typical probe current of 200 pA so there will be 6.25 x 1018 x 200 x 10-12 = 1250 million electrons per second or 1250 electrons every μs bombarding the sample.  Just shows how unimaginably small they are and how many of everything must move before we can even notice it.  Of course, the FIB also fires a current, just not the negative electrons rather the positive part of the atoms that are left once some electrons have been stripped.  They usually use Gallium ions because it melts below 30°C.  Its solid at room temperature but melts in your hand, unlike treats (now called M&M’s).  A proton weighs 1.6727 x 10-24, a neutron about the same at 1.6750 x 10-24 and an electron 9.110 x 10-28 so a proton is 1837 times heavier than an electron.  Gallium normally has 31 protons and normally 39 neutrons in its nucleus.  It therefore normally has 31 electrons in orbitals around the nucleus but if the electrons are stripped from the outermost shell (valance) it will become a little smaller and be positively charged.  Because only one electron is in the outermost shell of gallium it will have exactly the same charge as an electron but be positive rather than negative (1.6 x 10-19 coulombs).  So, each ion in the FIB will carry the same charge as each electron in the SEM but weigh about 1837 x 70 = 128,590 times as much.  So, you can imagine how much more momentum and damage a beam of ions can do to the sample surface compared to electrons.  That’s the same difference as an average man (70 kg) compared to a freight train with an engine and 63 loaded rail cars.

We started by measuring the features on a DMD (Digital Micromirror Device) using the SEM.

Image of DMD mirrors

The mirrors are about 13 μm square with a Ø1.5 μm hole and the gaps between the mirrors are about 1.1 μm.  So surprisingly we could get an array of 100 x 100 or 10,000 mirrors in a square of 1.3 mm on the side.

Well a DMD chip has several hundred thousand microscopic mirrors arranged in a rectangular array on its surface; each of which correspond to a pixel in the image displayed.  Each mirror can be individually rotated by around ±10° which represents an on or off state.  When on, light from the projector is reflected off the mirror, through a lens onto the screen as a bright pixel.  When off, the light is directed to a heatsink, so the same pixel appears dark.  To produce grey, the mirror is toggled on and off very quickly by pulse width modulation, so the shade of grey corresponds to the ratio of time on to time off.  To produce colour, three coloured projectors and three mirrors are required for each pixel and the ratio of on to off for each colour determines the pixel colour brightness.  The mirrors are made from aluminium and are mounted on a yoke which is connected to support posts by torsion hinges.  Because of the small scale, hinge fatigue does not usually cause a problem.

We did a few more experiments, carrying the acceleration voltage and the probe current etc, and then changed the sample for an EPROM and set up the FIB.  If you set the distance an M stage tilt correctly, its possible to be able to view the same part of the sample with the SEM and the FIB without changing the focus or moving the sample.  This is called the Eucentric point.  Below is the same image using both devices.Compare

TrapYou can see that the SEM is viewing the sample at an angle but there is a tilt correction mode if you like.  The resolution and contrast of the SEM is so much better than with the FIB.  Next we drew a trapezium on the sample that we were to mill out by setting the accelerating voltage and current just right we got a really nice cut of 3 microns deep.D200pSEM

We found the optimum current to be around 200 pA.  Its amazing how accurate and easy it is to machine the sample; this image is taken at 4000 times magnification.  The maximum optical lens you can use is about 1000 times.  This is just run of the mill, its capable of far greater magnification if you like.  When looking at biological samples, they have to be stained with a rigorous process prior to viewing so that the different tissue types stand out and can be seen.  When looking at anything else, you just put it in and focus; and the images are so much better than the ones I could get on my optical microscope as well.

GISOur next step was to inject a gas between the FIB and sample when it was scanning.  The gas we used was made from platinum organic molecules.  If everything is set correctly it will split the gas and deposit the platinum part on the sample while the organic part is vented away.  This time we drew a small rectangle on the sample as it takes a while.

Platinum deposit on EEPROM

We then decided to do the same cut, half on the deposit and half off.108

We noticed some funny furry deposit at the front of the cut so zoomed in for a closer look.Fur

This view was taken at 8200 time magnification and we could have gone in much further.  We then moved onto our last part where we analysed the surface at different places to do a spectral analysis and find out which elements were present.

Map Sum Spectrum
Spectrum of area around the cut out and deposit
Summary of elements at various places

The redeposit column was taken on the furry deposit which was found to be made up of platinum, silicon and carbon.  Basically, everything that was blasted away when the cut was made.  Its interesting that there is so much carbon around; I think the only place that could come from is the organic part of the gas which should have been vented away.  Not quite sure how it gets vented away anyway as everything happens in a vacuum and to vent away you need a lower pressure than where it is.  Well, you don’t get much lower pressure than in a vacuum.

Image inside vacuum chamber

Sorry its been so long since my last post but I have been so busy I cant tell you.  We have lectures all next week at Cranfield then the following week at Cambridge and then no more!  So once I have written up the reports for those I will only be doing my thesis so should have more time to catch up with everything else that has happened.  I will get there in the end.

NPL Realisation of SI Unit Definitions

I though that I should make it clearer exactly which of the SI units will be changed.  There are 7 fundamental SI units that all others are derived from.  This will probably be the biggest ever single change to our fundamental units since they started.  Great effort has been made to remove historical artifacts from our definitions because any variation in these artifacts change our standard to which everything else is measured against.  Its also very difficult to scale up or down from an artifact without further uncertainties creeping in.  It also means that as we get better and more accurate at measuring everything, the fundamental constants keep changing as they get more and more decimal places at the end.  If we fix the fundamental constants they will e forever constant and the unit definition can change getting more accurate with our increasing technology.  However, there are growing suspicions that our fundamental constants may not be absolutely constant after all, but this is not the place to be distracted.


The kg will change, and the Plank constant will be fixed forever at h = 6.62607015 x 10-34 Js exactly.


No change to the SI unit of length (m)

When this was previously changed, the speed of light was fixed forever at 299,792,458 m/s exactly.


No Change to the SI unit of time (s).

MOLE (mol)

The amount of substance (mol) will change by making Avogadro constant NA is 6.02214076 x 1023 mol-1 exactly.  The previously defined mass of carbon 12 will no longer be exactly 0.012 kg/mol.


The SI definition of current (A) will change, the elementary charge of an electron will be fixed forever at e = 1.602176634 x 10-19 C exactly.


The SI unit of temperature (K) will change, the Boltzmann constant will be fixed forever at k = 1.380649 x 10-23 J/K exactly.


No Change to the SI unit of light (cd).

Of course, many derived units will be affected by the redefinition’s, but great care has been taken so that all changes will lie within the area of uncertainty of the previously defined units, so it shouldn’t make any difference to any previous work.  All these changes will be approved during November 2018 and implemented on world metrology day on 20th May 2019.  No further changes are anticipated in the near or medium future after this date as all artifacts will have been removed and all fundamental units will rely on fundamental constants or atomic data.