Sunlight interacting with the Earth's atmosphere makes the sky blue. In outer space the astronauts see blackness because outer space has no atmosphere.

Sunlight consists of light waves of varying wavelengths, each of which is seen as a different color. The minute particles of matter and molecules of air in the atmosphere intercept and scatter the white light of the sun. A larger portion of the blue color in white light is scattered, more so than any other color because the blue wavelengths are the shortest.

When the size of atmospheric particles are smaller than the wavelengths of the colors, selective scattering occurs-the particles only scatter one color and the atmosphere will appear to be that color. Blue wavelengths especially are affected, bouncing off the air particles to become visible.

This is why the sun looks yellow from Earth (yellow equals white minus blue). In space, the sun appears white because there is nothing in between to scatter its white light.

At sunset, the sky changes color because as the sun drops to the horizon, sunlight has more atmosphere to pass through and loses more of its blue wavelengths. The orange and red, having the longer wavelengths and making up more of sunlight at this distance, are most likely to be scattered by the air particles.

The scattering of visible light by atmospheric gases is most correctly called the Tyndall effect, but it is more commonly known to physicists as Rayleigh scattering after Lord Rayleigh, who studied it in more detail a few years later. Rayleigh Scattering is where red, orange, yellow, and green are passed through and blue, indigo, and violet are "scattered" out creating the color.

Whichever direction you look, some of this scattered blue light reaches you. Since you see the blue light from everywhere overhead, the sky looks blue.

(*As for why the sky does not appear violet -- the wavelength most scattered -- see the explanation at the related link below.)

Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.
The sky appears blue to us because of the scattering of the blue light component of the light from the Sun. Some alpine lakes also appear a quite light blue colour for the same reason, light is scattered by tiny suspended flakes of minerals in the water.
Because the water particles in the air split the light and Blue light is dispersed the furthest that's why it creates the illusion the sky is blue

There are several options depending on the type of air pressure being measured:

• In the 1800's ships used a weather glass - a simple barometer - to measure changes in air pressure.
• To measure atmospheric (ambient air) pressure, a barometer is used. (It may be either an aneroid or a mercury type of barometer.)
• For tires, it's a tire pressure gauge.
• In industrial processes and boilers the gauge is frequently called a manometer.
• For pressure vessels it is a Bourdon gauge.

The 'normal' speed of sound is 340 m/s in dry air at room temperature and pressure.

From your question, it appears we should differentiate the terms "ultrasonic" and "supersonic".

Ultrasonic relates to sonic frequencies higher than 20 KHz, i.e. beyond audible range. For a given gas, the speed of sound is independent of the frequency of the sound measured and also independent of the density of the gas.

Supersonic relates to a speed of an object greater than the normal speed of sound (340 m/s in air at STP) and usually the phenomena associated with it.

The speed of sound is also a functionof the medium through which it's passing. For example, the speed of sound through water is 1,500 m/s, and is slightly over 5,000 m/s in iron.

So to answer your question, the speed of ultrasound in airis340 m/s for the reasons given.

Antimatter observes and obeys the same fundamental forces that matter does:

• gravity
• electromagnetism
• weak interactive
• strong interactive

Answer #1:

It's (1) divided by (the acceleration of gravity in the place where that mass has

that weight):

weight = mass x g (where g is the acceleration due to gravity)

⇒ mass/weight = mass/(mass x g)

= 1/g

On the earth, g ≈ 9.81 ms-2 ⇒ mass/weight ≈ 1/9.81 ms-2 ≈ 0.102 m-1s2

On the moon, g is approx 1/6 that of the earth, ⇒ mass/weight ≈ 6/9.81 ms-2 ≈ 0.612 m-1s2

If the questioner really meant weight divided by mass it gives the acceleration

due to gravity in that place otherwise I'm not sure of a use of knowing the

reciprocal of the acceleration due to gravity that the questioner asked.

=============================

Answer #2:

If you ask a scientist, that's true answer in the sense that a mass M experiences

a gravitational force Mg and if you measure weight in units of force (which

nobody does). But anyone else would be surprised to learn that a mass M (say

10 grams) would have a weight of anything else but M grams (10 grams).

Sometimes expressed as "grams weight" often just grams for short. If you pick

up a Kilogram, even a scientist would say "its weight is 1 kilogram". The

gravitational force on it is 1g, so if you let it go it will accelerate at a rate force

over mass, which is g. So the answer depends on your units of mass and weight.

That's why science lessons tend to avoid use of "weight". In outer free space

mass would be measured by (say) tension in the string if you whirl it on the end

of it around your head, but the weight (measured by a spring balance) would be

zero (precisely as described in the first answer above, with g=0).

==============================

Answer #2.1:

The problem with discussing mass and weight in the same units, and the reason that this masked contributor is waging a one-man battle to make the distinction recognized and acknowledged by users of this website, is the new problem that

you have now that the space age is here.

As long as we were all irrevocably bound to the Earth, one kilogram of mass would always weigh one kilogram, if you like it that way. We could afford to be sloppy about it, with hardly one out of ten men-on-the-street knowing or caring about the difference, and nobody ever had a problem with it.

But now that some of us have already slipped these surly bonds ... and among

the general population, the younger you are, the better the chance that you will

do so one day before you're done ... those who ignored the distinction begtween

mass and weight all through school, or never even encountered it there, are

poised to step into an inconvenient pile. Because as soon as you pack for your

trip to anywhere else away from Earth, and take along your lucky kilogram,

you're due for a shock when you step out at your destination: Your kilogram

doesn't "weigh" a kilogram there. It weighs something else. If you're on the

moon, for example, your kilogram weighs 0.165 kilogram ! That's the

shock I'm trying to avoid, because if you think the straight dope is too complex

for people to handle now, you haven't seen anything yet.

Acceleration

There are a few. The most famous is a = F/m, where F is the net force applied to a mass, m.

Acceleration is also the change in velocity, (Delta-V), divided by the change in time, (Delta-t). So, a =Δv/Δt.

For example, if an object's velocity changes from 10 meters per second to 20 meters per second in five seconds, its acceleration is (20-10)/5 = 2 meters per second per second, or 2 meters per second squared (m/s2).

For circular motion, centripetal acceleration is v2/r, where v is the linear velocity of the rotating object and r is the radius of its circular path.

Equations in a nutshell

a = (v2-u2)/2s

a = 2(s - ut)/t2

where

a=acceleration (m/s2)

v=final velocity (m/s)

u=initial velocity (m/s)

t=time (s)

s=distance (m).

OR

a=(v-vo)/t

a=acceleration (m/s2)

v=final velocity (m/s)

vo=initial velocity (m/s)

t=time (s).

Newton's Second Law

F = ma, thus, a = F/m

Centripetal Acceleration

ac = v2/r

Warning: Calculus Speak:

Acceleration is the second derivative of position with respect to time: d2x / dt2, which makes it the first derivative of velocity: dv / dt. Therefore, the acceleration is the slope of the curve on the velocity-versus-time graph.

Thus:

a = dv / dt = d2x / dt2

Acceleration is a quaternion with real and vector parts:

a= (V^2/R - cDel.v)) + (dcv/dR + cDelxv + V^2/R r)

a= (V^2/R - cV/R cos(v)) + (dv/dt + cv/R sin(v) + V^2/R r)

where R=ct and dR=cdt.

cv/Rcos(v) is the Centrifugal Acceleration a part of the real accelerations in the first parenthesis. The second parenthesis contains the vector accelerations.

Acceleration = F/m, where F is the net force applied to a mass, m.

a=f/m,

acceleration in terms of velocity.

a = v - u/t Delta Velocity divided by Time.

A = ΔV ÷ T Acceleration is worked out by (final speed - initial speed)/ time taken for change in speed a = v2-v1/ t2-t1 Strictly you should say velocity ie the speed in a certain direction. Youalso have the formula f=ma which tells you that the force needed to get something moving will be the mass of the object multiplied by the accelertion you want to achieve; so from this formula if you know force and mass you can work out acceleration. The formula for acceleration is: Vf-(Vi)/t ie. change in velocity per unit time. Instantaneous acceleration in its differential form is d2x/dt2 where x is a function of time t.

Acceleration is the time rate of change of velocity.

That is, acceleration =dv/dt (v - velocity ; t - time)

Or simply acceleration = change in velocity / time

Most commonly, a thermometer.

Related Information:

Thermometers are used to measure the increase or decrease in the temperature of a system as it gains or loses internal energy.

An alcohol-in-glass thermometer has been the most common personal instrument used to measure temperature. Mercury thermometers are still around but are no longer offered for sale. Today, digital devices are available that scan the forehead or ear. Some other devices used to measure temperature are:

Radiation pyrometer, for extremely high temperatures;

Glass thermometer: mercury or alcohol;

Thermocouple;

Thermistor (thermal resistor)

Bimetallic strip;

Bimetallic spiral;

Platinum resistance thermometer (a resistance detector);

Examples:

A mercury in glass thermometer uses mercury liquid contained within its glass structure to be subjected to heat.

the heat causes the mercury fluid to expand along the glass tube

and the total amount of expansion can be seen as a measure

along the accurate scale of indication.

This is a direct indication of the effects of temperature.

A more complex method of measuring temperature could be a

thermocouple measuring device.

A thermocouple consists of 2 dissimilar types of metal materials in the form of wires , which are joined at 1 end by weld/ fusion.

this single joined end is called the hot junction. The other end of the 2 wires are then terminated at separate junctions;

as in a electronic terminal block. This end of the 2 wires can be called the cold junction.

For most accurate temperature measure, I think temperature sensor is the first choice.