Want to ask something?
Send us an e-mail with the subject “Physics mysteries” to the address:
We can't wait to tackle your interesting questions!
Creation of vacuum by explosion
An explosion (e.g. a nuclear bomb) creates a pressure wave, i.e. air spreads outwards from the epicenter. Does this mean that a vacuum is created at the site after the explosion?
Yes, that’s right. A pressure wave is typically created by an explosion (it doesn’t matter what the source is) compressing the surrounding air. Because air is a flexible environment, this compression will spread further. You can try something similar yourself — just push water in a pool (or in a bath or pond) with your palm ...
Lift forces on an aerobatic aircraft
How is it possible for an airplane to fly horizontally during aerobatics, even when it is upside down? The lift on the wings should pull him down and not up…
It is true that the plane takes off due to the geometry of the wings. The upper part is more bulging than the lower part and therefore the air flows at a higher speed around the upper part of the wing than the lower part. And it follows from Bernoulli’s equation that the higher the velocity of the fluid, the lower the pressure at a given location ...
Hypothetical rescue in a falling elevator
Can I save myself in a falling elevator by jumping just before impact?
I hope that no one will have to experience this situation because it will not be possible to jump in a falling elevator — I will explain the situation where we do not take into account the air resistance. If an elevator falls, the elevator will move with the acceleration of gravity g (we won’t count air resistance) ...
Text in a car’s rearview mirror
Why is the ambulance sign on an ambulance reversed when looking in the mirror and it is clear that the sides of the displayed object do not change — what is to the right in front of the mirror i ...
A convex mirror is used in a car’s rearview mirror — this is the reason it always creates a reduced and inverted image. But the image that is created is reversed. If you want to shake your right hand with your image in the mirror, you will see for yourself. From our point of view, the hand is on the right, but in reality one would shake your hand from the left ...
How wide is the rainbow?
In addition to visible light, there are other components in the electromagnetic spectrum — ultraviolet and infrared, radio and X-rays ...
Light colour is made by its frequency and as you write correctly, light is a type of electromagnetic wave and is specific “only” by that it is about the frequencies we see. The frequency of the electromagnetic waves can be arbitrary and so our perception is limited to a narrow part of the spectrum (in frequencies 1014 Hz) ...
What would happen to a man inside a particle accelerator?
In the particle accelerator, particles collide at a speed close to the speed of light, creating a number of exotic particles ...
It could be expected that outside of sci-fi movies, we will not know how a human would end up if they were exposed to the current of really accelerated particles in the accelerator, but in the 1970s, something similar happened in Russia. Anatoly Bgorsky inserted his head into a proton accelerator because of a failure in the security device and beams of accelerated protons flew through his head ...
Is the electricity returning to the power plant?
If we build a simple electrical circuit, electric current flows from the battery into the bulb, turns it on, and then flows to the other pole of the battery ...
I will try to explain the question with an analogy of the postal services. We use electricity to fulfil its work and the post office to send packages. In the case of the electricity, charged particles (especially electrons, but also ions) do the work. At the post office, the postman does the work (in the case of Amazon, a drone is planned) ...
What color is the atom?
All things around us have some colour or they are for instance, transparent. But what colour are the atoms from which it is all made? First of all, we will distinguish what the possibilities are for a ...
The first possibility is that the thing (the Sun, a bulb, fire) emits light. In this case, the colour of light is determined by the material of the body and its temperature (so the Sun is yellow just because it consists of hydrogen and has a temperature of about 6,000 °C). Iron is orange during the casting just because it has a certain temperature and because it consists of iron ...
Why is my food heated in the microwave and not a plate?
When I put a cold plate of cold soup in the microwave, I take out a cold plate of hot soup in a minute. How does the microwave know what to heat?
The microwave oven is an example of an invention that was created not on the basis of a theoretical design, but happened by chance. While working on military radar components, Percy Spencer discovered that a chocolate bar in his pocket had melted. He researched further and the result was a microwave. Warm bodies differ from cold ones in that the molecules move faster in them ...
Can be anything colder than absolute zero?
The value of absolute zero is −273.15 °C. Could an object be cooled even more, for example to −300 °C? If not, why?
The very definition of absolute zero says that 0 K (i.e.−273.15 °C) cannot be achieved. It is one example of the limitations that nature gives us. Why this is so (that is, why nature limits us in this way) is more of a philosophical question but it can be shown in several cases that reaching absolute zero would be at least strange ...
Are there green stars?
Yellow, orange, red and blue-white stars can be found in space atlases. Could there be stars of other colours such as green?
Purely theoretically, I can’t see a problem with that. The colour of a star depends on its composition and temperature. The sun is yellow precisely because it consists mainly of hydrogen and also partly of helium and its surface temperature is about 6,000 °C. If we had hydrogen in a glass tube and heated it to the same temperature, it would glow yellow ...
Can astronauts make tea?
In the mountains, the air pressure is lower than at sea level which means that climbers can boil water before it reaches a temperature of 100 °C ...
The effect of atmospheric pressure on the boiling temperature can be imagined as water molecules trying to get out of the liquid. The higher the air pressure, the more air molecules are above the water surface and the more difficult it is for the water molecules to penetrate the air. So if the pressure is zero, water molecules could easily penetrate to the environment ...
Why is a tidal wave at the opposite side of the Earth than the Moon?
The tide is caused by the Moon attracting the Earth’s oceans. But why is a tidal wave on the opposite side to where the moon is where there should be the least amount of water!
You correctly describe that the tide is caused by the gravitational force of the Moon. The magnitude of the gravitational force depends, among other things, on the distances of the bodies. Therefore, gravity acts the most on the water on the near side of the Earth, and therefore, there is high tide ...
How many bananas can I eat so not to get radiation sickness?
Bananas are said to contain radioactive elements. How many bananas can I eat daily so I don’t get radiation sickness?
Personally, I wouldn’t be afraid that someone could die of a banana overdose. Although the “banana equivalent” is given as an auxiliary unit describing radiation, I do not think that its value reflects the real effect of the banana on the increase in radiation in our body ...
What is the shape of an electron?
In the schematic diagrams of an atom, electrons are usually painted as coloured balls. But how does an electron really look like?
Unfortunately, I am not a particle physicist, so I hope that I will not be fundamentally wrong in the fact that my answer is: we do not know. More precisely, we do not know and will not know. In our world (in terms of size) we are able to accurately measure, take pictures, and weigh anything. And as our technologies keep improving, we’re able to measure more and more accurately ...
Where does all the light go when I turn the lights off?
When I close myself into a room without windows and turn the light on, where does all that light go when I turn it off again? We could ask a similar question with sound (where does sound disappea ...
Like sound or waves in water, light is a wave, only in the case of light, it is an electromagnetic wave while sound is a mechanical wave. So if I describe the waves on the water surface, we can imagine the behavior of light in the same way. Instead of a room without windows, we will describe an arbitrarily large swimming pool with water ...
Why don’t airplanes flap their wings?
Planes were inspired by birds and all birds flap their wings when they fly. So why don’t planes flap their wings and they are fixed?
I have rather brief information about the history of flying but I think that the inspiration was based on the free flying of birds when they do not flap their wings (e.g. still used today by gliders). The principle of gliding (and therefore the flight of an aircraft) is different from flapping wings. When flapping its wings, a bird rises due to the fact that it bounces off the air ...
Can I make diamonds from coal at home?
Both coal and diamonds are made of carbon, only differently arranged each time. Is there a way in which coal could be turned into a diamond? Can diamonds be “cooked” on a cooker at home?
It is fascinating that the same element (carbon) has diametrically different properties only because of the different composition of the crystal lattice. But because there are the same atoms in coal, a pencil lead or a diamond, people wondered after the discovery of the structure of these substances (late 18th century) if a diamond could not be made artificially ...
Can I walk through the wall thanks to the quantum theory?
According to the quantum theory, the position and velocity of any particle is uncertain, so it may happen that the particle just finds itself somewhere other than where it was ...
It’s not that simple — more precisely, the degree of inaccuracy in determining the position and together with speed (momentum) is equal to a very small number (Planck’s constant). If the value of the Planck constant was in the order of hundreds of J ...
Could bacteria fly?
To move in a water environment, bacteria have various cilia and flagella that they move forward with but in the air, they are passive travellers depending on where the wind blows them ...
I am not a naturalist, so I would rather only physically speculate on this issue. I think it's simple — they don’t need to. Evolutionary theory (in my interpretation) shows that the evolution of animal species prefers those “modifications” of organisms that lead to their better development and survival ...
