Error in "Cosmos"?

Just happened to catch an episode today of Carl Sagan's "Cosmos" and I clearly heard him say that our radio broadcasts were leaching into the universe at the speed of light.
Now i havent read the book in many a year but hearing him say this got me thinkin(I do that sometimes). I seem to recall that all those science classes I took in school always referred to the speed of sound and the speed of light being different. Wait it gets better.
Here's the thing. when i watch tv it appears that the sound and the light get to my receptors at the same time. And what of the delay between signals from our satellites out in the solar system and ground control.
So was that an intentional slip of the tongue,typo in the script?
Could our radio waves once they leave the atmosphere pick up speed.
I wanna know.
Talk amongst yerselves.

There is an extremely simple explanation to your question. Radio waves are electromagnetic waves. These travel at the speed of light. Radio waves are not sound waves.

when i watch tv it appears that the sound and the light get to my receptors at the same time.

That's because even though the speed of light (and radio) is much higher than the speed of sound, both are still fast enough to travel the distance between your TV and you in a fraction of a second.

If you want proof that sound and light do not travel at the same speed, wait until the next thunderstorm and listen. If it is sufficiently far away, you will see flashes of lightning, then a pause, then hear the thunder.

Could our radio waves once they leave the atmosphere pick up speed.

They actually would get slightly faster, but for a different reason. The speed of electromagnetic waves, such as radio, depends on the medium it is travelling in. EM waves travel a little bit faster in vacuum than in air (less than 1% faster)

That is a very good question, do not let out of view this is that a radio wave and all waves lose frenquency over distance and so on. So is a radio wave that leaves our atmosphere to relay with a satellite pic up speed? logically yes, but between the time of breaking the atomosphere and the bonce off the relay can it speed up or will between that distance? I would say when this radio wave breaks the gravitational pull it no longer has gravity affecting it and the wave can possibly travel faster.

Thanks Dragon I forgot about the lightning thunder difference.
Dont think I"m clear yet though On why theres a delay between us and our space probes. I mean if the're radiowaves and not sound waves then why the time descrepancy.
That was my thinking. That because it was a vacuum things might speed up.
Also I would still like to know what you think Sagan meant by that comment.

[edit on 13/12/05 by longhaircowboy]

As Dragons pointed out the "radio waves" are not sound, they are electromagnetic waves - light waves at a lower frequency, so they travel the same speed as light. Once these waves are converted to sound at your speakers - then they slow down.

Concerning the delay in telemetry between us and space probes; the light from the sun takes 8 minutes to get to us. That's 98 million miles. Mars is about 56 million miles so it would take about 4.5 minutes to get a transmission from Earth to a probe on Mars.

Hope this helps.

Radio waves travel at teh speed of light. They''re Electro-magnetic radiation, just like visible light. A EM waves travel more slowly than their maximum, the speed of light, when moving through a medium. So I would think that the waves travel more slowly when moving through the 'viscous' medium that is the atmosphere, and then are less 'restrained' when moving through space. But even space isn't a perfect vaccuum, and these differences, the slow down, are incredibly small I'd figure.

But those technicalities aside, the waves are travelling at the speed of light. THey're moving as fast as, say, a beam of light from a flashlight.

edit to add:
er I mean 'they move billions and billions of centimeters a second pas billions and billions of particles'.


The Cosmos re-airing is neat, its nice that they have the new graphics too.

[edit on 13-12-2005 by Nygdan]

Because of the huge distances involved. The Solar System is a big place and light takes time to get from A to B.

Distance from Sun to Earth is 1 Au = 149 598 000 km

the speed of light = 299 792 km / second

299,792 km / second * 60 = 17,987,520 km / minute

149 598 000 km / 17,987,520 km / minute = 8.3 Minutes for light from the Sun Reaches earth. Radio Waves are no exeception they cannot exceed 17,987,520 km / minute

It is true that these waves are electomagnetic in nature and travel at the speed of light. well why havent we been heard, well they lose strength as they travel and eventual become part of the electromagnetic jumble in space. So in order to receive them, they would have to have a powerful electromagnet, and be able to filter out the trash, and at a point the waves become too weakened to be of any use.... So only that ship passing through or near our solar system might be able to pick them up.

Hehehe... physics noob

It's okay though. You see, light isn't instantaneous - just very very fast. In fact, it takes 8 minutes for light from the surface of the sun to get to Earth. Light travels at about 300,000,000 (three hundred million) metres per second. The speed of sound travels (on average) 340 metres per second... so as you can see, it takes a lot longer.

In fact, if a sound wave were to (somehow) come off of the Sun and make it to Earth, it would still take 211764706 seconds to reach us! That's almost 6 years and 8 months!

So now you see just how huge the difference is, eh?

As for light, light is actually just the electromagnetic wave that we can visually see with our eyes. Radio waves, gamma rays, X-rays, Microwaves, cosmic rays, and all of those are in fact just other types of electromagnetic waves - in many ways, light is almost the only thing we use to measure things at a distance! And that's because it's so fast!

Hope this helps you understand things!

Thanks everyone for your wonderful responses.
But I would still like to hear your responses on whether thats what Carl meant or not. What say you?

Originally posted by longhaircowboy
Thanks everyone for your wonderful responses.
But I would still like to hear your responses on whether thats what Carl meant or not. What say you?

Umm yeah, I've seen Cosmos a tons of times and even though it is outdated alot of the stuff about the EM Spectrum is still pretty much accurate.

As for it leaching out into space yeah it's doing that allthough it hasn't gotten that far yet, when was the First broadcast again? It can't have gotten out for more then 100 Lightyears and the chances of anyone picking up and reconizing them are slim. Only what 15,000 Stars within 100 ly radius I believe.

[edit on 13-12-2005 by sardion2000]

[edit on 13-12-2005 by sardion2000]

Originally posted by longhaircowboy
Thanks everyone for your wonderful responses.
But I would still like to hear your responses on whether thats what Carl meant or not. What say you?

Yes, that's what he meant. We're screaming Pat Robertson and Howard Stern in 360 degrees into space...

isn't that a great thought!

Ah, what Carl Sagan was saying is that, since we transmit our TV shows and radio programs via radio waves - and since those waves travel out from the radio and TV towers in all directions - that some of those waves are travelling into space rather than travelling back to earth, or to our TVs.

Think of it as a ripple in a pond. The centre of the ripple is the TV tower, and the waves are radio-waves. Notice how they keep on spreading out further and further from the centre.

And, like the pond example, after a certain distance, it becomes almost impossible to distinguish the waves that you created, from the waves that were already naturally there. At this point, the waves are simply too diluted to get anything useful out of.

The same happens with our radio signals. They travel out, deep into space. If anyone does catch any of it, it'll only likely be a single bit of the static of the television screen.

On that note - roughly 4% of the image scramble on a TV set to a channel with no reception on it (TV static) is radio-waves left over from the Big Bang. So remember, the next time someone says there's nothing on TV, just remind them that they can always tune into the creation of the cosmos!

What seems cool about EM waves is that they can go through matter and light just seems to bounce off or curve around matter. Does this mean an EM wave would be better than light waves, as in fiber optic compared to direct EM connection or in that light goes through the atmosphere pretty clean and the EM waves do with friction?


imagine.gsfc.nasa.gov...

This site talks about the different types of waves and the ways they transfer energy across the atmosphere and space.

this picture shows an equation that is very helpful in seeing the spectrum of light to wavelength for energy.
imagine.gsfc.nasa.gov...

Yeah Val and that aint even the tip of the iceberg. I cant stand reality TV so what must those catchin it on the fly think.
Love you guys.

Promytheus, light is an EM wave. Radio, Microwave, all of that are EM waves. It's just that the frequencies of these waves brings them into the categories we've defined for them. Also, once certain boundaries are reached with the frequencies, new and different affects come up.

For one, the shorter the frequency, the more "powerful" the wave. Gamma rays can go through a foot of concrete! Their energy is such that they are not easily stopped by normal matter. Light, on the other hand, can be absorbed by many materials. However, take a sheet of plastic. Notice how you can see through it? This is because not all of the EM waves are being absorbed by the plastic - some continue to pass right through!

However, other waves are even weaker than light - such as Microwaves, and Infrared waves. These things can be blocked by almost anything. However, this in turn creates another unique phenomenon. For one, these waves can be directed (since metals totally repel microwaves, the microwaves can actually reflect off instead of being absorbed!), and two, since they're easily absorbed - and since energy in a closed system must remain the same, they transfer their energy to that which absorbs them - making the item hot!

So, wonder why they use red light to keep food hot? It's because red light reflects enough light for you to see the food, but also makes the food absorb more energy from the light, and so makes them hotter!

I should start teaching physics...

Reminds me of galaxy quest.

If you want an even more dramatic example of the difference between the speed of sound and light, go see the Space Shuttle launch in person (if it ever happens again). You're so far away from it at the public observation site, you see it launch and well clear the tower before you hear the first rumbles of the engines igniting. Pretty amazing.

So lets put it like this, we all know light is faster than sound and as fast as Em waves and still we can even inderstand how it is so fast. Is it possible that light is an element that is creates its own set of laws and forces. I have been wondering if you had machine shoot a beam of an EM wave inside a sphere going at light speed would the beam inside travel at light speed or would the EM wave go faster than light and escape the sphere.

Originally posted by promytheus
I have been wondering if you had machine shoot a beam of an EM wave inside a sphere going at light speed would the beam inside travel at light speed or would the EM wave go faster than light and escape the sphere.

These sort of thought experiments around relativity make my head hurt....

I believe the sphere couldn't reach light speed as it has mass (I presume), and it's mass will tend towards infinity as it's speed approaches light speed...so it could only approach light speed and never reach it. Their are loads of such mind boggling thought excerises associated with Einstein's theories.

Is it possible that light is an element that is creates its own set of laws and forces

It is certainly very weird. For example is light a wave or a particle? Err, both:

It can be shown that light has a wave nature, due to wave characteristics such as frequency and wavelength, which relate to the color of light. It can also be shown that light has a particle nature, since an individual light particle (photon) can be detected experimentally. Thus, light exhibits wave-particle duality.

From: en.wikipedia.org...