Science and Astronomy Questions
Posted: 22 Jun 2018 07:19
Watsisname, thank you for the explanation, It's still a complex subject for me. Although I have already read some physics books, I only started to interest myself recently.
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Watsisname wrote:Propulsion Disk: It's okay. I appreciate that you want to help explain things! There is some skill for knowing how confident to be in an answer or not, which comes with experience, and yet still is never perfect. Misconceptions especially can be tough. We all make mistakes, the best thing is to learn from them!
Aside: Just for fun, let's compute how far your depth perception works by parallax:
The average distance between a human's eyes is about 63mm (and slightly more for men than women). The minimum angle that the human eye can resolve is also around 1 arcminute (1/60 of one degree).
The distance at which the shift in angle due to a 63mm separation of your eyes is 1 arcminute is:
So beyond a few hundred meters it is impossible to discern distances directly with your eyes using parallax. You can however gain more distance perspective if you are moving (like driving down a highway) as your motion makes things shift against the background. Having an intuition for the true size of objects also helps with judging distances, though this is also easier to fool.
If we instead set the angle to 1 arcsecond (1/3600 degree), and the baseline distance to 1AU, then we recover the definition of the parsec used in astronomy, which is about 3.26 light years. 1 parsec is the distance at which the parallax angle for a 1AU shift in perspective is 1 arcsecond.
Gnargenox wrote:Source of the post If time is relative to any gravitational field the observer is in how do we know the true age of anything closer or further away from us?
Propulsion Disk wrote:Source of the post Thanks Watsisname! But what happened to your mathcode? it was there and then it disappeared.
Propulsion Disk wrote:Source of the post Do cold temperatures increase when pressure is added to it? Because I held my cold cup and put pressure on it and it got WAY colder!
midtskogen wrote:Source of the post Heh. I've never thought of timing of light as an explanation of stereo vision. But it does have a grain of sense in it, indirectly. We have stereo hearing, and though stereo hearing doesn't primarily work that way, it's should be biologically possible to take the timing into account to help locating sound sources. I wonder if any animals do this (or even humans). Could this be important for bats, for instance?
In the Inferior colliculus, a structure in the bat's midbrain, information from lower in the auditory processing pathway is integrated and sent on to the auditory cortex. As George Pollak and others showed in a series of papers in 1977, the interneurons in this region have a very high level of sensitivity to time differences, since the time delay between a call and the returning echo tells the bat its distance from the target object. While most neurons respond more quickly to stronger stimuli, collicular neurons maintain their timing accuracy even as signal intensity changes
A single echolocation call can last anywhere from 0.2 to 100 milliseconds in duration, depending on the stage of prey-catching behavior that the bat is engaged in. For example, the duration of a call usually decreases when the bat is in the final stages of prey capture – this enables the bat to call more rapidly without overlap of call and echo. Reducing duration comes at the cost of having less total sound available for reflecting off objects and being heard by the bat.
The time interval between subsequent echolocation calls (or pulses) determines two aspects of a bat's perception. First, it establishes how quickly the bat's auditory scene information is updated. For example, bats increase the repetition rate of their calls (that is, decrease the pulse interval) as they home in on a target. This allows the bat to get new information regarding the target's location at a faster rate when it needs it most. Secondly, the pulse interval determines the maximum range that bats can detect objects. This is because bats can only keep track of the echoes from one call at a time; as soon as they make another call they stop listening for echoes from the previously made call. For example, a pulse interval of 100 ms (typical of a bat searching for insects) allows sound to travel in air roughly 34 meters so a bat can only detect objects as far away as 17 meters (the sound has to travel out and back). With a pulse interval of 5 ms (typical of a bat in the final moments of a capture attempt), the bat can only detect objects up to 85 cm away. Therefore, the bat constantly has to make a choice between getting new information updated quickly and detecting objects far away.
Microbat range in frequency from 14,000 to well over 100,000 Hz, mostly beyond the range of the human ear (typical human hearing range is considered to be from 20 Hz to 20,000 Hz). Bats may estimate the elevation of targets by interpreting the interference patterns caused by the echoes reflecting from the tragus, a flap of skin in the external ear.
Stellarator wrote:Source of the post - An alien civilization more technologically advanced then us somewhere in the Milky Way galaxy, light-lag permitting and barring non-technological life being found.-FTL travel being possible or completely impossible.How might the discovery of one, affect the other in non-obvious ways (ex. NOT "the aliens know about FTL, and give us the tech")? I was thinking that though the mathematics behind physics are standard throughout the observable universe, it is philosophically possible that our concept of numbers is subjectively species-bound (and perhaps then self-crippling in our viewing of the universe?), and thus might an alien civilization race develop some parallel to our Math that their brains find objective proofs for in the observable universe, that allows for mass to transport faster then light without infinite energy?
Stellarator wrote:Source of the post I was thinking that though the mathematics behind physics are standard throughout the observable universe, it is philosophically possible that our concept of numbers is subjectively species-bound (and perhaps then self-crippling in our viewing of the universe?), and thus might an alien civilization race develop some parallel to our Math that their brains find objective proofs for in the observable universe, that allows for mass to transport faster then light without infinite energy?