That’s the title of a famous paper by philosopher Thomas Nagel. But you don’t have to be a philosopher to wonder about the question. A reader writes:
My 10 year old asked me this questions and since I think you are a bit
of a science fan, I thought I might ask you.Can a bat ‘see’ a stealth bomber with its radar or would it fly right
into it?What do you think?
I’m not an expert here, but I’ll be happy to conjecture (perhaps other readers can fill-in/correct the details via collective brainpower).
It seems to me that the answer to the question depends on two things: (1) how fast the stealth bomber is flying and (2) whether its surfaces reflect, deflect, or absorb sonar.
The sonar issue is key, because bats have sonar (echolocation by sound waves), not radar (echolocation by radio waves). Because sonar is dependent on the speed of sound (not light) the first question is also relevant.
If the stealth bomber is flying faster than the speed of sound then the sound waves from the bat will not have the chance to reach it before that bomber flies into/past the bat, so it won’t see the bomber coming. (NOTE: Stealth bombers usually fly below the speed of sound to avoid creating a sonic boom that they can be tracked by.)
If the stealth bomber is flying slower than the speed of sound then the sound waves from the bat will have the chance to reach it before the plane flies into/past the bat, so the bat might be able to see it (see below). However, the plane is probably so loud that the bat might not need sonar to see it. It might just hear it coming. (That is not to say it would be able to get out of the way in time; bats fly way slower than the speed of sound.)
If the stealth bomber is standing still and turned off (e.g., on a runway, in a hangar) then the speed and noise of the plane wouldn’t matter, leading us to the question of whether the surfaces of the plane reflect, deflect, or absorb sound waves.
The way stealth technology works in planes, such aircraft are made of and covered with materials that absorb radar but not sonar. These might not help hide a plane from a bat. However, not all the radio waves used in radar are absorbed by the plane, so its surfaces are shaped and angled in such a way that they deflect radio waves so that they won’t echo back to radar station. The angle and shape of theser surfaces might also deflect sonar (I don’t know). But even then, the stealth craft’s "invisibility" is not pefect. What the advent of stealth technology did was allow us to reduce a plane’s radar signature to the size of an insect but not to eliminate it entirely.
Bats, however, are good at spotting things the size of insects (that’s what a lot of bat species eat). Also, the angle of the surfaces on a stealth aircraft only deflect stuff from certain angles. Therfore, my guess is that if a plane were sitting still and a bat were flying around it, the bat probably could see it with sonar.
For what it’s worth, I Googled the question of stealth technology and sonar and found references to stealth submarines designed to thwart sonar underwater, but these might not work against bats as water has acoustic properties that are quite different than air (the medium in which bats’ sonar is designed to work).
What stealth bombers can fly above Mach 1?
You just NEVER know what topic is going to come up here. 🙂
Stephen, I agreed. that’s why I’m always a wee bit excited everytime I click Jimmy’s blog 🙂
Are you suggesting the bat might try to *eat* the stealth bomber? 🙂
What stealth bombers can fly above Mach 1?
None. In fact, even the stealth fighter’s top speed is subsonic.
I am unaware of any stealth aircraft that fly faster than the speed of sound but wanted to take care of the theoretical possibility of what would happen if one were flying that fast.
I am unaware of any stealth aircraft that fly faster than the speed of sound but wanted to take care of the theoretical possibility of what would happen if one were flying that fast.
Reminds me of “Firefox”.
Stealth Aircraft and Human Dignity
In “What Is It Like To Be A Bat?” Jimmy Akin mentions that a stealth bomber would have to fly under the speed of sound to remain undetectable; sonic booms are pretty conspicuous, after all.
It’s been over ten years since my time in the USAF, but if I recall correctly, the stealth fighter’s main focus was its almost diamond-like faceted design which would deflect radar in ways that parallel what happens when you shine a light into a cut diamond (or a disco ball ;-). The stealth *bomber* focused more on the skins — the materials — that absorb radar frequencies. I Am Not An Aeronautic Engineer(tm) nor do I play one on TV, but that was my recollection.
I always love Jimmy’s brief science and language diversions. Perhaps it’s because of my engineering background. I especially liked last week’s discussion of early man’s running ability. Keep up the great work, Jimmy! Both on the air and in your blog…
Actually a bat would probably have a pretty good chance of hitting a ‘sub outta water,’ cuz they’re entirely covered in several inches of what is essentially rubber (Designed by Goodyear no less) that reduces all sound reflected from them.
I think the answer is in general a “Yes” to a bat being able to “see” a F-117 or B2 plane. As Jimmy alluded to absorption effect only works on a range of frequencies of radio waves (i.e. light). Obviously, you can see a B2 with the naked eye, so it does not absorb all frequencies of light like a Klingon Bird of Prey. The bouncing effect only works with certain frequencies as well. Sound is not light, so it is affected differently. The profile of the stealth places also makes it hard to see it flight, making it harder for an enemy to judge its vector of pursuit.
BTW, I believe the SR-71 Blackbird uses some stealth-type technology and it is the one the fastest planes ever created.