Funny question?

[XFool]

Today, on Radio 4's PM, Martha Kearney(?) asked Dr. Monica Grady(?) words to the effect: "Can you feel any sense of speed in space".

I thought this a rather peculiar question. What do others think?

[DiamondEcho]

I get some sense of speed in an aeroplane. I can see why having such a sense of movement might be on consequence to a person.
Almost none of us know what it's like to fly through space, so perhaps almost any first hand description is of value towards trying to conceptualise it?

[XFool]

Well, I am currently sat here in front of the telly, while I am travelling at about 66,000mph. Feels OK to me.

My point was that surely, when you are dealing with space travel, by now some sense of the meaning of 'speed' should be appreciated, even in the media? Or am I being too fussy?

Galileo, thou should be living at this hour! Or possibly not.

[AJC5001]

Well, I am currently sat here in front of the telly, while I am travelling at about 66,000mph.

Relative to what?


Adrian

[XFool]

Well, I am currently sat here in front of the telly, while I am travelling at about 66,000mph.

Relative to what?

Well, isn't that the point?

[Clitheroekid]

"Can you feel any sense of speed in space".

I would think it depends entirely on how fast you're travelling and how close you are to a visible object.

If you're travelling at 100 mph 20 feet above the Martian surface I'm sure it would appear pretty fast. But if you were half way on a journey from the Sun to Proxima Centauri, even if you were travelling at 10 million mph you would probably be unaware that you were moving at all.

[UncleIan]

Surely you get a sense of speed when the stars start making lines and smear past the cockpit with rising electronicy whooshy noise?

[XFool]

I would think it depends entirely on how fast you're travelling and how close you are to a visible object.

If you're travelling at 100 mph 20 feet above the Martian surface I'm sure it would appear pretty fast. But if you were half way on a journey from the Sun to Proxima Centauri, even if you were travelling at 10 million mph you would probably be unaware that you were moving at all.

Agreed to that. I should perhaps have explained that the original question was framed in the context of the Cassini mission.

To be sure, there is possible ambiguity over the exact nature of the question asked. But on the other hand I am used to hearing BBC correspondents declaring excitedly that: "Astronauts will be working outside the ISS while travelling at 18,000mph!" - I always think: "And this matters how?" By that I do not mean I am unimpressed by the ISS etc itself. The astronauts being no more bothered that they are "travelling at 18,000mph" than I was to see my car last being serviced while moving at 66,000mph (at least). Not that I didn't have concerns, but that is another matter!

I guess what I'm trying to say is: journalists have got to grips (to some extent!) with the fact that ships made of iron float on water; craft heavier than air stay up in the air; voices and images can be mysteriously transported invisibly and silently large distances through space. Surely the concept of speed as a purely relative phenomenon - the mainstream of the physical sciences for ooh!, four centuries? - is an idea whose time has come? Even in journalism.

And when you think we are living in the century after Einstein...

[stewamax]

If you were travelling at a constant speed in a straight line - no.
But if your InterGalactic Voyager* was on a curved path, you would feel a sensation of 'motion' the same as if Voyager was accelerating or braking in a straight line, and this would be so whether or not the spaceship had windows.

* - powered by surplus VAG diesel engines

[colin]

There is no sense of relative speed, the brain creates an image or sensation if you like out of sensory input and the context in which we experience that input, so when we are sat in a train at a station with a train next to us we are unable to tell which train moves when one pulls away, the brain through the eyes has received information to prove one train is moving relative to the other but without further visual signals there is no context to decide which one is actually moving (relative to the other)
The sense of speed that you mention i suspect is more correctly termed a sense of acceleration,in an accelerating train we can feel pressure from the back of the seat in addition to the usual downward/upward pressure of the Earths gravity, in a zero gravity environment acceleration is indistinguishable from gravity, in that in an accelerating space craft astronauts will experience the back or the floor of the craft move towards them until it is applying pressure to their bodies, whether they interpret this as speed i guess depends on the context within which the mind interprets this pressure but the actual sensory input is ambivalent, there is no difference between acceleration and gravity.
In an orbiting spacecraft the astronauts are in free fall , that is in a never ending plummet towards the earth and so experience floating weightlessness.
What do the actual astronauts say?

[Clitheroekid]

If you were travelling at a constant speed in a straight line - no

I disagree. It all depends on the environment in which you are travelling.

As I mentioned in my earlier example, if you're travelling at 100 mph 20 feet above the Martian surface it will seem fast, whether or not you're travelling in a straight line.

If you object that this isn't `space travel' then you can extend the principle to say that if you were passing, say, the moon of a planet at 100,000 miles an hour and at a distance of 1,000 miles you might still get a sensation of speed.

But if your movement couldn't be judged by reference to any visual objects there would be no sense of speed, no matter how fast you were travelling.

The sense of speed that you mention i suspect is more correctly termed a sense of acceleration

No, speed and acceleration / deceleration are entirely different, and bear no relation to each other. You can feel exactly the same degree of acceleration travelling at 100,000 mph as at 100 mph.

[stewamax]

If the spaceship had closed windows and was travelling at a constant speed in a straight line, an occupant would have no sensation speed or movement (or - by definition - acceleration or deceleration).
To change this either:
- the ship would have to accelerate or decelerate (or move in a curved path - which is equivalent)
or
- the windows would have to be opened

[colin]

the windows would have to be opened

Now just who would open the windows?