If you're interested and live in Britain, I advise you to watch this before it disappears. The next one's on tomorrow night.

Among other things, it explains how it is that we can distinguish the past from the present and the present from the future. That being entropy, the only principle in physics (and one of the most important generally, see thermodynamics) that requires a particular direction for time.

BM, for one to understand, you unfortunately must use the concept.

Think like this, does the past exist? No. Because there is no physical or material evidence that it does or has done. Also time cannot be edited. So then why can we change the past. For example, if a man dies with no family or friends or acquaintances. He effectively ceases to exist so long as all evidence of his existence is destroyed. So did this man ever exist at all, for surely the 'past' defines old existence.

When the past existed, it was the present. It happened. If you're asking me to explain time without using tenses then we're going to have a problem.

so there is no way of estimating the speed of our galaxy?

I watched one video from a site which I can't remember and am not sure if it is accurate, that said that hubble saw galaxies moving faster than the speed of light, if this is true than It would be safe to assume that our galaxy and those galaxies are moving in opposite directions as faster than light speed is thought to be impossable, in which case we could calculate that our galaxy is going faster than a certain speed

note: this is speculation based on a questionable source

I suppose we would. But how can the past exist if how we remember it differently. Surely the past is an enormous concept of thoughts and recollections. Time should be solid yes?

@LDG - I think you may have got it wrong, as far as we know it is impossible to travel at the speed of light because the closer you get, the harder it becomes to reach that speed. Something like things around you slow down.

Time is solid, no-one said that man's recollections and trustworthiness of past events were.

But then the whole time is relative thing becomes void. Time is a man-made concept and therefore time is relative to the human mind and the past, human recollection.

On Earth we measure speed relative to the ground. The ground itself is very much moving, but you can't account for that in traffic court. The motion of the Earth is measured relative to the Sun, the motion of our solar system is measured relative to the galactic centre. I suppose it is possible that all the galaxies in the universe are speeding along in the same direction, but there's no way you could prove it one way or the other. We can only measure the movement of the galaxies relative to each other. Usually relative to ours, since all the light we use to detect other galaxies is collected from this one.


You're confusing the map with the territory. Our memory of the past is a (highly questionable) recording of a tiny piece of it from the perspective of one person. It is not the actual past, insofar as there "is" one.

I have no idea what we should and shouldn't expect to observe based on the hypothesis of "solid time".

It's nothing to do with time dilation. The energy required to move particles with mass exponentially increases as the speed of light is approached.

There you have it.

Perhaps time would be better based on something solid, unchangeable and measurable rather than in seconds, minutes and hours. We even base our measurements of time on a calender that applies only to our planet, and even that is innaccurate. So a terran day is useless on Venus, Saturn, Pluto etc.

You're arguing from way off base here. You cannot judge the thing being measured by the unit of its measurement. Indeed, you have completely combined the two in your mind. We can use anything to measure the passage of time, regular astronomical occurrences specific to Earth are the most useful. The Venusian calendar is no more use to us here than on Mars, but neither is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the Cesium-133 atom, which is constant everywhere (and is in fact the definition of the second and is used in atomic clocks) except for all the time dilation that occurs in the universe. Time isn't based on our measurements of it! Time already is, and would still be without any humans, as it was before us and will be after us. Our units are for our own convenience and application. They are our map. The territory already existed.

I still don't know what you mean by "solid time". You won't get unchangeable time anywhere, it is slowed by both very high gravity and very high speeds, but only relative to another location without such high gravity or speed. When approaching a black hole you would not notice time slow down, but if you get back out of it you'd find that everyone else's clocks (and even dates) have advanced further than your own. That's how you'd measure it precisely, in any case. Hang around longer and everyone you know will have grown grey in the hair and long in the tooth by the time you return.

The arrow of time always points from the past, which had lower entropy, to the future, which has higher entropy. When time has been slowed down by the gravity of a black hole entropy will be increasing at a slower rate, though from your perspective there will be no difference. The advanced progression of entropy will be written in the faces of your friends when you return, but from their perspective there has been no change of rate for anyone but you. But you might think that they sped up time by removing themselves to a region affected by a reduced gravitational field.

I know it is impossable to travel faster than light, what I meant was that if they found a galaxy that looked like it was we could assume that our galaxy was moving in the opposite direction at greater than a certain speen.

for example: if they found a galaxy that was travaling 1.25 times the speed of light reletive to us then it would be safe to assume that our galaxy is moving at greater than 0.25 times the speed of light in the opposite direction

about the time thing, denying it's existance would be like denying that you have done things, are doing things and will continue to do things, denying time is like denying existance

i remember arguing about time with BM before.

i lost. in fact, i sorely remember having my arse handed to me.

I'm just not going to try any more for said reasons.

Didn't a couple of German scientists break the speed of light through quantum tunnelling? Or was that a load of bullshit?

The only example I heard was light waves propagating in a Caesium vapour, which was able to give the appearance of exceeding the speed of light on a vacuum without actually doing so.

What BM said, except I don't think it was actually a light wave. As far as I understand it (and I really don't), actual matter did not breach the speed of light, but a pressure wave (or something equivalent) passing through the Caesium vapour did.

In all honesty the science was well above my pay grade.

DON'T SAY THAT

I CAN'T HANDLE CHANGE

I'm still trying to grok Bayesian rationality. I fear that will be a lifetime's endeavour.

you lost me at 'grok'.

i feel better for that.

To grok. It's a Martian word from Stranger in a Strange Land. In the context I'm using it, it's like "to understand" or "to comprehend", but turned up to eleven and multiplied by itself several times.


It also means "to drink", so everyone can use it.

I understood every concept in that on an individual word basis.

I failed to understand the sentence.

I'm still working on it. From what I've seen, it's superior to traditional rationalism, insofar as traditional rationalism helps people to make novel and more interesting mistakes.

What are the chances of there being some wierd alien species of fish swimming around in the methane lakes of titan?

What are the chances that I will ever touch a vagina that I didn't pay for again?

Bad.

What about a weird alien species of vagina swimming around Titan?

It could happen.

Long.

That'll just give you more time to spend with u- ooh, I'm beginning to see the problem.

That shit's thicker than water. Apparently rainfall there is meant to be quite nice and alien, the raindrops of methane fall like snowflakes.

One of the Jovian moons, Europa, may hold promise, it has water underneath it's thick ice crust, though the chances of life thriving in such a dark, cold place may be slim.

If there's liquid water, it won't be cold.

But the iiiiiiiiice man...

The iiiiiiiiiiiiiiice is cold.

Tell that to frozen lakes.

Cold from our point of view. But go to the poles, where the water is zero degrees Celsius or less, and you'll find it is teeming with life. Go to a black smoker on the sea bed, where the water can reach 300 degrees Celsius, and you'll find life there as well, thriving without even any energy from the sun.

Liquid water is inhabitable.

How can the water be 300 degress? I don't mean that like as in sarcasm, generally how, it's so weird!

Magic, in some form, can do anything.

The pressure at the sea bed, which is considerable, keeps it liquid. Pure water only boils at 100 degrees Celsius in the average atmospheric pressure present at sea level. As you climb in altitude the pressure drops and the water is able to boil at lower temperatures. That is why you can't make a good cup of tea up a mountain: the water boils at too cool a temperature so cannot become hot enough to open up the tea leaf cells. Similarly, pressure cookers allow you to boil food at a higher than 100 degrees Celsius by maintaining a high pressure within the cooker.

hm i was reading something about ice 7 ice made by pressure,they say it can be hot as fire and it will still be icy,quite wierd

Ice Ih is the kind you get on Earth under normal conditions, with a hexagonal crystal lattice that forms snowflakes and is less dense than liquid water in the conditions available on Earth. Under specific laboratory conditions and quite probably on other worlds other crystalline phases of water are produced (Ganymede is thought to be mostly made of Ice II). Ice Ic is occasionally known in the upper atmosphere and Ices II-XV have been produced under a range of pressures and temperatures. The water molecules arrange themselves into different structures with different properties.

There's also amorphous ice which lacks any crystalline structure at all.

This is the phase diagram, pressure in Pascals on the y axis, temperature in Kelvin on the x axis.

there are a few good documentaries like journey to the edge of the universe,i watched it 3 times,and lost planets( i dont quite remember the name of this documentary)it says that on some planets it can rain molten iron,or you can find planets with diamonds the size of a small tower,or even bigger.it also said that there are planets and stars running a drift trough the universe till they find a home,mostly this happens when a bigger star enters the system and slingshots a other star out of the system.some scientists say that these planemos can have life if they had lots of CO2.

edit: i think its this
http://channel.nationalgeographic.co...ideos/07059_00

I wouldn't count on an orphaned planet being life-bearing. While it's possible, the chances are probably the chances of finding an Earth-like planet, squared, and applied those odds only to orphaned planets. Which are hard enough to find as it is. It'd be like finding a needle in a hundred billion exploded haystacks, in which there is a light year between each piece of hay and the needle is made of straw. In the dark.