6 minute read
Health & Science
Ever wondered why the grass is green, a tomato red or the sky blue? Why are the oceans of the world blue?
While science can explain them both, the reasons for each are entirely di erent.
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Most of us, upon learning that the skies and oceans are blue, hear the myth that “one is blue because it re ects the other”. is is not true. e sky is blue because of how atmospheric scattering works, sending blue light in a variety of directions more effectively than red light, causing blue to arrive at our eyes from a variety of directions. e oceans, meanwhile, preferentially absorb certain colours more than others, so as you go to deeper depths, the blue light is the last colour that remains.
When the Sun is high overhead, the sky towards the zenith is a much darker blue, while the sky towards the horizon is a lighter, brighter cyan colour. is is due to the larger amount of atmosphere, and the larger amount of scattered light, that is visible at low angles on the sky.
Schematic animation of a continuous beam of light being dispersed by a prism. If you had ultraviolet and infrared eyes, you’d be able to see that ultraviolet light bends even more than the violet/ blue light, while the infrared light would remain less bent than the red light does.
Rayleigh scattering a ects blue light more severely than red, but of the visible wavelengths, violet light is scattered the most.
It’s only due to the sensitivity of our eyes that the sky appears blue and not violet. e longest wavelength and shortest wavelength visible lights experience a di erence in Rayleigh scattering by nearly a full order of magnitude. From very high altitudes in the pre-sunrise or post-sunset skies, a spectrum of colours can be seen, caused by the scattering of sunlight, multiple times, by the atmosphere.
Direct light, from close to the horizon, reddens tremendously, while far away from the Sun, indirect light only appears blue. e discovery of the Earth from space, with human eyes, remains one of the most iconic achievements in our species’ history. Apollo 8, which occurred during December of 1968, was one of the essential precursor missions to a successful Moon landing, which will celebrate its 50th anniversary this July. e Earth’s oceans may appear blue, but along the continental shelves, they appear a lighter shade of blue than in the deepest parts of the ocean. is is not an artifact of the way the image was constructed, but a real phenomenon that details the di erence between what’s absorbed and re ected by the ocean itself at various depths.
If you descend down into a body of water and only allow your surroundings to be illuminated by natural sunlight from above, you’ll nd that everything takes on a bluish tint, as red light is the rst to have its wavelengths absorbed away entirely.
At deeper depths, when the sea is illuminated by natural sunlight from above, not only red colours but oranges and yellows begin to disappear. Even lower down, greens will be absorbed, too, leaving only faint blue light to be observed.
As seen from space, planet Earth is often described as a pale blue dot, but it’s only the liquid bodies of water — dominated by Earth’s oceans — that appear blue-hued. e continents, clouds, and ice caps don’t appear blue at all; it’s the oceans, not the atmosphere, that give our planet its overall complexion. For thousands of years, humanity had to simply accept these properties of our world as facts. But with the advances of modern science, we understand why both the skies and oceans are blue.
Contrary to what you might have read, there’s no one single factor responsible for Earth’s blue skies. e skies aren’t blue because sunlight has a blue tint; our Sun emits light of many di erent wavelengths, and that light sums up to be a net white colour.
Oxygen itself isn’t a bluecoloured gas, but rather is transparent to light.
However, there are a myriad of molecules and larger particles in our atmosphere that do play a role, scattering light of di erent wavelengths by di erent amounts. e ocean plays no role in the colour of the skies, but the sensitivity of our eyes absolutely does: we do not see reality as it is, but rather as our senses perceive it and our brain interprets it. ese three factors — the Sun’s light, the scattering effects of Earth’s atmosphere, and the response of the human eye — are what combine to give the sky its blue appearance.
Mammy, why is the sky blue, and the ocean too?
Breakthrough with new cancer-killing virus
A new cancer-killing virus, known as Vaxinia, which has seen successful tests in animals, has been injected the rst human patient, according to scientists.
It’s easy to hear the word virus and instantly think of something bad. After all, there are a lot of deadly viruses out there. However, scientists are using the new cancer-killing virus Vaxinia in an experimental cancer treatment. e hope here is that the virus will amplify the body’s immune response against cancer. e virus itself has been engineered speci cally to kill cancer cells. And, in previous animal trials, scientists have seen very promising results. ese kinds of viruses have been a ‘smoking gun’ in the ght against cancer for over a century.
However, the success of these viruses has been very limited, to say the least. is time around, though, the scientists have engineered the cancer-killing virus to not only harm cancer cells, but also to make them more recognisable to the body’s immune system. Researchers hope that this will help make the body’s response stronger, allowing it to ght back better.
Previous clinical trials of cancer drugs have shown promising results, too. But, Vaxinia could help open new doors, too.
Of course, before moving on to the human tests, the scientists tested the virus on animals. In many cases, they saw huge success at shrinking tumours in early animal and lab experiments. e cancerkilling virus has shown that it can reduce the size of lung, breast, ovarian, pancreatic, and colon cancer tumours.
With that success, the scientists decided to move on to human testing. Results seen in animals do not always directly translate to human patients. ere are a lot of reasons for this, obviously, but the researchers are hopeful this virus could improve patients’ chance to ght back against cancer.
Currently, Vaxinia will be tested in a Phase 1 trial of just 100 cancer patients. ese patients have metastatic or advanced solid tumours, and each has tried at least two other treatments. e researchers plan to administer the drug in two di erent groups. e rst will receive just Vaxinia. e second group will get the cancerkilling virus plus an immunotherapy drug.
Phase 1 trials are mostly about safety and nding the optimal dose. As such, it might not prove the e cacy of the virus as a whole. However, it is an important next step in possibly nding an alternative method to ghting cancer. e trial is currently expected to complete by early 2025. So, it’ll be a while before we see any nal results.
