so i was watching a video on alexander and his conquests and this question came to my mind. how did they cary their pikes ? since they were so big it would be uncomfertable to just walk with them. and its not like they could have just put it in their supply trains since they were already tight on space. so how did they do it ?
The usual method for marching with pikes was to carry them at an angle, on the shoulder. Other large weapons, such as halberds, muskets, and big two-handed swords, were carried in the same way on the march.
https://i.pinimg.com/564x/d8/b6/e2/d8b6e2eec9ae6e341c32122ee104ec9d.jpg
https://i.pinimg.com/564x/a6/d2/cf/a6d2cf81bc5d5ed5fef2ec1d8054e863.jpg
Modern re-enactors have shown that this works:
https://commons.wikimedia.org/wiki/File:Pikeniere_Wallenstein-Festspiele_Memmingen.jpg
https://commons.wikimedia.org/wiki/File:Musketeers_and_Pikemen_EC2_-geograph.org.uk-_1037515.jpg
Cavalry would often carry their lances similarly on their shoulder:
The main concession to the pike being longer than those other weapons is that they were often carried at a shallower angle (i.e., less upright):
which lets the soldiers march through gates, under trees etc., more easily. It has the disadvantage of needing more space between successive rows of pikemen (to allow room for the butts). It also makes it harder for them to them to turn (i.e., change direction), since the pike needs to be swung horizontally, and can also easily clash with other pikes (thus, on the battlefield, pikes were often carried upright to avoid these problems). Soldiers with other weapons would also often carry them more horizontal when not marching in a close formation:
https://i.pinimg.com/564x/e3/33/9c/e3339c4da5efb08eb14d27917b80c5ba.jpg
https://i.pinimg.com/564x/89/0d/25/890d25a52488754e23e207e8fd97eba4.jpg
When stopped, the pikes would typically be rested on their butts on the ground, vertical or almost vertical:
https://i.pinimg.com/564x/eb/73/89/eb7389fe5071ad2744528954b8fde2ad.jpg
https://i0.wp.com/streetsofsalem.com/wp-content/uploads/2013/04/pikemen-fogg.jpg
https://i0.wp.com/streetsofsalem.com/wp-content/uploads/2013/04/pikemen-029.jpg (see https://streetsofsalem.com/2013/04/08/pikemen-on-salem-common/ for this and the previous drawing)
Note that pikes weren't, on average, heavier than halberds and big two-handed swords, and they were lighter than muskets (and also lighter than the heaviest halberds). While pikemen might not have liked the weight (typically 2-3kg), pikes were light enough to be carried easily enough. Their length could be a problem, but I already noted the solutions above (almost-horizontal carry and more space between rows for easier marching on the road, and vertical for easier maneuver on the battlefield).
The above examples are of pikemen much later than Alexander's pikemen, but their pikes were probably similar in weight to later pikes. With no surviving Macedonian sarissa hafts, we don't have a definitive reconstruction, and diverse reconstructions have been proposed. These include some really heavy pikes, using a large spearhead from Vergina which was (almost certainly) mis-identified as a pike head, and the mystery "coupling sleeve" (also from Vergina) which is often assumed to join the parts of a two-piece pike. Noting that later pike heads (which are definitely pike heads, not misidentified) are usually quite small, the large Vergina head is almost certainly not a pike head - the general principle is that the larger the spear, the smaller the head (at least when considering large two-handed spears). The large Vergina head also had a socket diameter that would have meant that the pike haft near the head would have been really thick - this is the part of a pike where you want to keep the weight as low as possible. Also, since later pikemen marched with one-piece pikes, there was no need to use a "coupling sleeve" to break a pike down into two pieces for easier marching. For a good discussion of the sarissa and its parts, see
One of the few clear depictions of a Macedonian pikeman in art shows a not-too-heavy weapon (with a haft much thinner than the large Vergina head socket), and no sign of a coupling sleeve:
(The head appears quite large (I estimate about 18-20cm, not counting the socket), which is larger than the 10-15cm usually estimated for sarissa heads from other art.)