The light from a star twinkles as it passes though a gas. Spaceships use the ejection of gas to manoeuvre. Would the stars not twinkle through the lateral thrusters? How much gas would be visible before it was dissipated into the vacuum of space?
Proposal Discussion Do Stars Not Twinkle?
- Thread starter G.T
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The light from a star twinkles as it passes though a gas. Spaceships use the ejection of gas to manoeuvre. Would the stars not twinkle through the lateral thrusters? How much gas would be visible before it was dissipated into the vacuum of space?
Lots!
The twinkling is caused by the differential refraction of the light through differently dense materials. The refractive index of those materials has to be high enough to cause an appreciable change in the direction of the light as well.
Any gas in a vacuum would dissipate so quickly that there would not be any appreciable refractive index contrast, except *very* close to the vent.
By the way, the reason why gas dissipates is that the individual molecules are travelling very fast due to thermal kinetic energy. The speeds involved are large percentages of the escape velocity from Earth's gravity at room temperature. Indeed, for hydrogen and helium the molecular speeds at room temperature are above Earth's escape velocity, which is why they're able to escape the atmosphere and be lost into space.
They do, but their angular width is large enough that you don't see the effect as greatly. Stars, on the other hand, are effectively point sources and hence the effect is more marked.
If you look at Jupiter, Saturn etc. through a telescope you will see them wobbling, as if looked at through a flowing stream. On a night with a particularly high degree of atmospheric disturbance, such as the high level wind of the jet stream blowing above you, you can hardly make out any detail at all on Jupiter as it looks as if you're looking at it through a babbling brook.
Exactly. Even with something as close as the Moon, it will look like you're looking at it through water when you zoom up close. This is all about warm air currents in the upper atmosphere, and it's a major reason why astronomy is typically a winter sport as the air is cooler. Astronomers talk about having "good seeing", which is as much about the air temperature as how many clouds are in your way.
Actually, the worst seeing is when the jet stream is blowing, which isn't technically a warm air current. This can actually be worse in winter as generally it's a lot further south (and generally slap-bang over the UK).
Correct.
What about comets ?
Since it is mostly their trail which is visible, they should be quite bright when looked at from a position in space, shouldn't they ? I imagine they are, because the light from their trail isn't absorbed by atmospheric dust when seen from space, so they could be quite the eye-catcher.
On another note, I think it could be cool if asteroid fields could feature some dust for some time after they have been visited. It takes rather long I would guess if dust was raised (literally
) until it is caught by the asteroid's gravitation again. So I would use dust in space to show when I get near asteroid fields which have been worked at and leave it out in free space.
This would give some sense of motion in densely (asteroid-) populated areas but on the other hand leave a stronger feeling of emptiness in free space.
Since it is mostly their trail which is visible, they should be quite bright when looked at from a position in space, shouldn't they ? I imagine they are, because the light from their trail isn't absorbed by atmospheric dust when seen from space, so they could be quite the eye-catcher.
On another note, I think it could be cool if asteroid fields could feature some dust for some time after they have been visited. It takes rather long I would guess if dust was raised (literally
) until it is caught by the asteroid's gravitation again. So I would use dust in space to show when I get near asteroid fields which have been worked at and leave it out in free space. This would give some sense of motion in densely (asteroid-) populated areas but on the other hand leave a stronger feeling of emptiness in free space.
They explained the dust streaks by saying its part of your HUD which also (I assume) appear on your upper and side views as well? Guess one could test that by powering off the HUD at speed and seeing if they vanish.
At least you have the option to force them off. I understand their purpose and value to the masses, but after a while, I tend to find them more distracting than they are worth.
If they have streaks going past you to represent <500m/s, I wonder what they will come up with to represent space bending supercruise.
At least you have the option to force them off. I understand their purpose and value to the masses, but after a while, I tend to find them more distracting than they are worth.
If they have streaks going past you to represent <500m/s, I wonder what they will come up with to represent space bending supercruise.
Well of course, I meant whilst landed on a planet following the planetary landings update. Ahem.