Space & Science

[Dirk Gently]

I thought we could do with a thread for Jason, Jon & Emma to talk about science & 'stuff'. Also to for we proles to ask questions & such.

The first question isn't that hard, is anyone joining me in watching the Shuttle Atlantis launch to repair the Hubble space telescope?

Apparently it is the final mission, 11 days in duration. It has just taken off & has now reached the correct height for orbit.

[Fate]

i read this is considered a very risky mission. the new mode of op for the shuttle until retirement is to fly it near the international station to avoid another atlantica disaster. don't know why hubble is supposed to be so good for viewing anyhow. being in orbit it cann't be that much closer to what it views. or is it to avoid light pollution?

[Dirk Gently]

It is so it has an undistorted view of deep space. Viewing through our atmosphere distorts & restricts what can been seen. All of the deep space images (as far as I'm aware) of any quality are from Hubble.

[Jason Thompson]

i read this is considered a very risky mission. the new mode of op for the shuttle until retirement is to fly it near the international station to avoid another atlantica disaster.

Endeavour is sitting on the other pad at Cape Canaveral waiting to go up on a rescue mission if required.

don't know why hubble is supposed to be so good for viewing anyhow. being in orbit it cann't be that much closer to what it views. or is it to avoid light pollution?

It's not about being closer, it's about being a) above the atmosphere and b) being able to sit and watch the same spot for hours on end. None of the images you see from Hubble could have possibly been captured from Earth, and given the amount of information those images have yileded I'd say it's one of the best scientific tools we have.

[Jason Thompson]

And to answer the original question, no I didn't watch the launch. I tend to follow the missions via news reports rather than watching live events. The sad fact remains that watching a lot of live space broadcasts is very dull.

[Paul Monk]

I've always wondered this, but I remember reading ages ago that the space shuttles rely on computer gear that hasn't been updated since the 80's. Therefore they use computers that are vastly underpowered when compared to home pc's. I also read that NASA have to source spare electronic parts from ebay.
Does anyone know if this is true or is it a load of balls?

[Paul Clement]

I know Jason and I had a conversation about NASA budgets before, and yes if I remember correctly they do not have the most up to date equipment that one would expect them to have. I'm not sure how that pans down to their computer systems though.

I do feel that the impetus disappeared once the cold war ended. There was a very real race to space between the Soviet Union and the U.S that resulted in both nations pushing the boundaries. Now that there is no real competition, perhaps it's unsurprising that it has become a lesser priority. It's a shame really, as great strides were made in short time during the 50's, 60's and 70's.

[Jason Thompson]

I've always wondered this, but I remember reading ages ago that the space shuttles rely on computer gear that hasn't been updated since the 80's.

This is pretty well true. However:

Therefore they use computers that are vastly underpowered when compared to home pc's.

Comparisons between multifunctional home PCs and single function dedicated systems are on very shaky ground. Home PCs have to do a lot with fancy user interfaces, multi-purpose software, and various things that generally go unused. When you're flying a shuttle the ability to produce photorealistic images and provide a fancy mouse pointer is somewhat irrelevant. The question is not the power or memory but whether or not it can do the job. The Apollo Guidance Computer had less memory than a pocket calculator does these days, but it was perfectly adequate to operate a lunar spacecraft.

It is also worth bearing in mind that given a choice between state of the art new technology and proven older technology, the older technology can often win out, especially when something as critical as the lives of seven people depend on it.

I also read that NASA have to source spare electronic parts from ebay.

I doubt they have to, but it might be a good source of parts. It doesn't matter too much where the parts come from as long as they work.

[Paul Monk]

Cheers Jason.

[Jason Thompson]

Another thing that I forgot to mention is the importance of not getting hung up on the idea of things having to be 'up-to-date'. The shuttle computer system may be 20 years old, but it works, and works well. Neither of the two shuttle disasters had anything to do with the computer. The fact that all bar one of the shuttle missions ever flown has been successfully guided down from orbit to landing by the onboard computer is a testament to how robust the system is (and the one that failed did so because there was a gaping hole in the wing, which the computer couldn't have done anything about anyway). Updating the computer system would require a huge program of research and devlopment to make it operate the existing shuttle systems and prove that it can do so reliably. If it ain't broke, don't fix it.

[Paul Monk]

Quite right. The more complex the system the more prone it is to going wrong. My C64 is probably far more robust and problem free than my laptop!

[Si Hunt]

Is it true that time, like space, although a dimension of itself, also has dimensions of its own, and because the energy radiated by a light neutron is equal to the energy of the mass it absorbed, mass has light and energy?

Si.

[Jason Thompson]

Only in the minds of scriptwriters, as far as we know.

[Andrew Curnow]

I heard that in electrokinetic theory space expands to accomodate for the time necessary to encompass its dimensions.

More seriously, I was very interested to read all that stuff about the shuttle computers. I have this lovely image of newbie astronauts complaining about the poor font options on their display screens...

[Captain Tancredi]

I also read that NASA have to source spare electronic parts from ebay.
Does anyone know if this is true or is it a load of balls?

I've heard a similar story about London Underground, which is rather more plausible.

[Andrew Curnow]

To be fair, a lot of our machines at work are a bit on the old side, and our first port of call for any repair parts is always eBay.

[Fate]

on the subject of computers i know that until quite recently computers on jet planes only had about 64kB of memory. a modern aircraft might be designed to live 35 years+ but in that time will only update the computer once or twice which seems silly. a friend once told me the russian space shuttle which flew was much better than the us space shuttles but i cant remember why

[Dirk Gently]

But as Jason intimated, an aircraft has a dedicated memory so what it has it uses for one purpose only. If it only needs 64K of memory then that's all they give it. Whether the aircraft has a life of 5 years or 35 is irrelevant if that is all the memory the aircraft needs then thats all it gets.

[Fate]

so little memory they cant even install windows on the space shuttle. thats probably a good thing

[Jason Thompson]

on the subject of computers i know that until quite recently computers on jet planes only had about 64kB of memory. a modern aircraft might be designed to live 35 years+ but in that time will only update the computer once or twice which seems silly.

A computer on a jet only has to fly the jet. 64kB of memory is easily enough to do that. When computers first came to be, programmers had to be very creative to make them work with very limited memory. These days, memory has become cheap and mass-produced, meaning that in most cases computer programmers are not limited by the availability of memory. That's why so much memory in your computer can be dedicated to fancy graphics and quality sound, and running systems checks constantly in the background without slowing down your game playing or video downloads too much. Indeed, computer systems are so easy to produce they are now being used to operate things that work perfectly well without them. Washing machines, for example. We tend to be a bit complacent about the use of computers now, but we did manage to live very well without them once.

A computer system on a jet has to fly the jet and it has to do it reliably. If it does, there is no need to update it. The first jets and even spacecraft had no computers at all, but they worked. There's no point in updating a computer system just for the sake of it.

a friend once told me the russian space shuttle which flew was much better than the us space shuttles but i cant remember why

Primarily it was lighter (so could carry a heavier payload) and had a slightly different wing design that reduced drag.

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[Rob McCow]

A computer system on a jet has to fly the jet and it has to do it reliably.

I suppose there's also the problem with complexity. The more complexity that is introduced into a system, the more likely it is that something can go wrong. Modern computer games are notorious for bugs and glitches. And if you're flying a jet, I suppose you don't want a fail error in any line of computer code. If you have 64 lines of code, it's easier to debug than 64,000 lines.

[Jason Thompson]

Precisely. The last thing a pilot wants to see at 40,000ft is 'this jet has performed an illegal operation and must be shut down. Would you like to send an error report?'

[Paul Monk]

Or the pilot mucking about on Facebook.

Another question. What exactly is dark matter? Is it real? How is it detected? (My understanding is that its impossible to directly detect) Or is it just a convenient fudge invented by scientists so they can get the correct amount of mass in the universe so that their equations for the rate of expansion of the universe work?

[Jason Thompson]

As far as I know it's hypothesised to explain the apparent discrepancy between gravitational action on the universal scale and the amount of visible mass present, but I'll defer to Emma on that one.

[Paul Monk]

A fudge then?

And deferring to your missus is the way it should be