NASA's Perseverence Rover Landing on Mars ...
Phil Pilgrim (PhiPi)
Posts: 23,514
... today 11:15 a.m. PST
Watch the action here:
https://mars.nasa.gov/mars2020/timeline/landing/watch-online/
-Phil
Comments
SUCCESSFUL LANDING!
That second by second landing update got my heart racing to a nail biting successful landing. What a relief. Well done NASA team.
This is twice now that they've used a sky crane to lower a lander onto the surface. The first time I was thinking, "What could possibly go wrong with that complicated approach?!!" I guess, by now, we can call it a proven technique.
-Phil
Unbelievable achievement! I watched Curiosity land too. This was just as nerve wracking.
I wish I had really been there!
Just goes to show doesn't it, that Perseverance pays off.
Watched it live on my phone. NASA and SPACEX have these landings down.
Watched it live too. Not as exciting as watching Apollo 11 tho.
It was around 9 minutes or so delayed due to the distance - makes you think doesn't it!
So by the time we knew it was successful it could have gone horribly wrong.
Was nice to see pics of mars ground quickly after the confirmed successful landing. Did you see the guy (or was it an alien) holding up the big photograph in front of the camera
Maybe it was instantaneous and communication to Mars takes 18 minutes?
I'm just sort of joking. Apparently the speed of light can only be measured in round trip time. We can't prove light isn't instantaneous in one direction. (This is one of the unsolved mysteries in physics. )
I have a hard time believing the direction makes a difference but it's fun to think the messages and video arrive instantaneously.
(Apparently this is the type of comment I make when up past my bedtime.)
That's one thing I don't like about space movies that involve the planets. The astronauts always have real-time conversations with their counterparts on Earth. But I suppose one has to cheat to keep the narrative alive.
-Phil
Consider these musings:
1) At 99.5% the speed of light, time dilation is about a factor of 10. So the 3 minutes and 22 seconds it takes for a photon (laser communication) to reach Mars from our perspective, only took the photon 20 seconds from its perspective.
2) Airplanes traveling between the same two airports in the US travel faster in one direction than the other because of the Jet Stream. Does photons traveling between Earth and Mars travel faster from Earth to Mars than Mars to Earth because of the stream of photons shooting out from the Sun?
It's first image!
https://mars.nasa.gov/resources/25596/perseverance-rovers-first-image-from-mars/
No.
-Phil
Second image!
https://www.nasa.gov/image-feature/jpl/perseverance-s-first-full-color-look-at-mars
Here it is during landing, suspended from the sky crane:
https://www.nasa.gov/sites/default/files/styles/full_width/public/thumbnails/image/rover_drop.jpg?itok=Szjpa6ka
-Phil
Photons do not experience passage of time. From their perspective they are gone the instant they are created, regardless of how many billions of years they have been traveling.
No. Just like radio waves are not sped up or slowed down by other radio waves. Although there was a recent video by a popular YouTube channel that claimed that it is impossible for us to know if there is a "preferred" direction for the speed of light. Saying that the speed of light could be faster in one direction than the other but we can never know because we need to measure the speed of light via a round trip. I think that if there was a difference it would be apparent in the CMB (Cosmic Microwave Background).
For more info about the speed of light through the "ether", look up the Michelson-Morley experiment on Google.
-Phil
Here's your Uber, Bernie.
@"Phil Pilgrim (PhiPi)" I've been looking for more recent light speed experiments conducted in space out beyond the Van-Allen belt. Are you aware of any?
@"Phil Pilgrim (PhiPi)" This is an impressive shot!
I was thinking it would be funny if the first images showed a sign stuck in the dirt saying 'NO OVERNIGHT CAMPING'.
I remember when the first rover landed someone posted a cartoon of an alien with a color printer printing pages to hold in front of the camera. Think it may have been used (later?) in a printer ad for HP??
For a long time now, the speed of light has been defined as a constant. So any experiment to "measure the speed of light" is now really a procedure to establish how long a metre is.