You hear the question: Would you rather fight 10 duck sized horses or a horse sized duck? Or something similar. Everytime its asked, someone says, "according to the inverse square/square cube law, the horse sized duck would be very weak". Someone explain the physics here. Ive heard it said with inverse square and square cube, whichever is the correct one is the one i mean.
I have watched multiple videos but can't seem to wrap my head around it.
From what I gather, the further the object is from the light, the softer the fall off and the less light is actually lost.
Wondering if anyone can confirm this - I understand the basics of the inverse square law but seems everyone refer to it based on distance alone. My question is about light source size:
If distance to subject remains the same and light source power remain the same, will a small modifier output a higher intensity on the subject than a large modifier of the same type, due to spreading out the light? Will a small soft box read brighter than a large one on the subject at the same distance and power?
Thanks in advance.
So in a vacuum light can go on forever, but on earth because of atmosphere light depreciates in intensity over distance, noticeable at 1 meter (3.3ft) away… can someone elaborate on why/factors etc? Thanks
Hi All,
I am working on a simple model of an ionisation chamber in a room of air and concrete. I am varying the distance from the source to see what the kerma dose is, but I'm not getting the readings I would expect, the dose is coming out lower than it should be. I am using the EGS kerma environment with an isotropic source. Is there something I am doing wrong? Thanks for the help.
A moon landing denier (ugh) is telling me that because of this law, the moon would be way too bright to land on, because at its surface the light would be 15,500,000,000 times more intense (that number is a direct quote).
Obviously that isn’t the case lol. So does this inverse-square law apply to the moon or not? How exactly does this work? Lol
I know that the law applies to point sources, but I’m not sure if the moon is a point source of light.
But yeah, thanks for reading! Help would be greatly appreciated :)
The universe is expanding, right. But scientists can't figure out how fast. It's called the Hubble tension.
https://www.livescience.com/hubble-constant-crisis-deepens.html
https://www.scientificamerican.com/article/hubble-tension-headache-clashing-measurements-make-the-universes-expansion-a-lingering-mystery/
https://skyandtelescope.org/astronomy-news/tension-continues-hubble-constant/
When the universe expands, distances increase, and that make everything late for their appointments.
Buuuut..... if the universe wasn't expanding, and the photon just slowed down, it would look like distances are increasing.
Here is the graph I made showing the acceleration of expansion from the Supernovae Cosmology Project data.
https://mikehelland.github.io/hubbles-law/img/sn_expanding.png
Hubble's law rewritten as an inverse square law, v=c-c/(1+HD)^2, matches the "acceleration" curve using a constant H0=0.04 Gly-1.
Method
According to Hubble's law, objects move away from each other proportionally with distance.
Model 1: v=HD
One feature of such a universe is that the travel time from one place to another increases with distance. If you were to shine a laser toward a target 100 million light years away, it would take longer than 100 million years for the laser beam to reach the target. The expansion of space moves the target farther away, meaning the light has new space to travel through, which takes more time.
https://mikehelland.github.io/hubbles-law/img/vcHD.gif
An alternative cosmology that can produce the exact same time delays without the expansion of space requires that the photon will indeed lose energy and speed during intergalactic journeys. If a photon loses speed when it redshifts, its travel time to a target in space will also increase, despite the target remaining stationary. This cosmology is shown in green in the image above, given by a variation on Hubble's law:
Model 2: v=c-HD
Since model 1 and model 2 produce the exact same time delays and redshifts, they are both in conflict with the observation that the expansion of space is accelerating. There appears to be more redshifting in the nearby universe than farther away
https://iopscience.iop.org/article/10.1086/300499/fulltext/
To address this in the standard model of cosmology, a new concept is introduced called dark energy. This has the effect that Hubble's constant isn't actually constant, but cha
... keep reading on reddit ➡Just a general question. Just a bit confused as to how the diffuser can make a specified pattern like a rectangle let’s say and not break the law.
I was watching a JRE interview with Brian Greene and they were talking about how people figured gravity would cause the universe's expansion to slow. But to my mind, since gravity gets exponentially weaker with distance, wouldn't the lessening gravity be loosening its grip and allowing the universe to expand faster?
I'm sure astronomers have considered this, I just can't find anything about it.
Thanks
Inverse-square: gravity, electrostatics, etc.
Inverse-cube: magnetic
I hope this is OK to post here. It's something that I find really useful to remember when adjusting my light heights -
The amount of ENERGY that a light can hit your plant with is less and less the further away the plant is from the light. That's obvious. But the thing is, it is related to the squared value of the actual change in distance.
If you DOUBLE (increase by 2) the distance between your plant and light, you decrease the amount of light energy by a factor of 4. No big deal, right? If you TRIPLE the distance, you decrease the energy by a factor of 9. That can be a huge deal. But this is also important - the Inverse Square Law applies to the light from the source, but not really to the HEAT. Because the heat from the light or anywhere else isn't always made up of radiant energy.
It is also important to remember when decreasing the distance between the light and your plants- like when your plants start to shoot up or you want to max out flower development - if you go from 24 inches to 8 inches (decreased distance by a factor of 3) you just increased the light energy by a factor of 9. That means that suddenly those leaves are getting 9x more light energy. That can burn a half-grown bud pretty fast.
I know this info is out there and probably common knowledge to a lot of growers, but most of the growers I know either go by strict, fixed distances based on what they read somewhere, or they use a PAR meter or LUX substitute. I feel like the fixed distances are too generic, or specific to exact models/types of lights, while I can't afford a PAR meter.
My workaround is to listen to the plants, and keep that Inverse Square Law in mind.
Here is the graph I made showing the acceleration of expansion from the Supernovae Cosmology Project data.
https://mikehelland.github.io/hubbles-law/img/sn_expanding.png
Hubble's law rewritten as an inverse square law, v=c-c/(1+HD)^2, matches the "acceleration" curve using a constant H0=0.04 Gly-1.
Method
According to Hubble's law, objects move away from each other proportionally with distance.
Model 1: v=HD
One feature of such a universe is that the travel time from one place to another increases with distance. If you were to shine a laser toward a target 100 million light years away, it would take longer than 100 million years for the laser beam to reach the target. The expansion of space moves the target farther away, meaning the light has new space to travel through, which takes more time.
https://mikehelland.github.io/hubbles-law/img/vcHD.gif
An alternative cosmology that can produce the exact same time delays without the expansion of space requires that the photon will indeed lose energy and speed during intergalactic journeys. If a photon loses speed when it redshifts, its travel time to a target in space will also increase, despite the target remaining stationary. This cosmology is shown in green in the image above, given by a variation on Hubble's law:
Model 2: v=c-HD
Since model 1 and model 2 produce the exact same time delays and redshifts, they are both in conflict with the observation that the expansion of space is accelerating. There appears to be more redshifting in the nearby universe than farther away
To address this in the standard model of cosmology, a new concept is introduced called dark energy. This has the effect that Hubble's constant isn't actually constant, but changes with time:
Model 3: dark energy
The alternative cosmology offers other options. In model 2, the speed of a photon begins at c and decreases with distance. It does this by subtracting HD from c. But there are other ways to do this. It could divide c by (1+HD). The photon would still start at c, and it would still decelerate with distance. Just along a different curve.
This opens up a whole new class of hypotheses to try. One of them, an inverse square law, produces a decent fit of the data from the Supernovae Cosmology project:
Model 4: v=c / (1+HD)^2
In this model, H is still constant throughout time, however it has different units. The line shown is using a value of
... keep reading on reddit ➡